diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonNextgenClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonNextgenClientCodegen.java
index 376dc40786f..2685fde8dbb 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonNextgenClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonNextgenClientCodegen.java
@@ -64,6 +64,11 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
 
     private String testFolder;
 
+    // map of set (model imports)
+    private HashMap<String, HashSet<String>> circularImports = new HashMap<>();
+    // map of codegen models
+    private HashMap<String, CodegenModel> codegenModelMap = new HashMap<>();
+
     public PythonNextgenClientCodegen() {
         super();
 
@@ -404,6 +409,8 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
      * @param typingImports typing imports
      * @param pydantic pydantic imports
      * @param datetimeImports datetime imports
+     * @param modelImports model imports
+     * @param classname class name
      * @return pydantic type
      *
      */
@@ -411,7 +418,8 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
                                    Set<String> typingImports,
                                    Set<String> pydanticImports,
                                    Set<String> datetimeImports,
-                                   Set<String> modelImports) {
+                                   Set<String> modelImports,
+                                   String classname) {
         if (cp == null) {
             // if codegen parameter (e.g. map/dict of undefined type) is null, default to string
             LOGGER.warn("Codegen property is null (e.g. map/dict of undefined type). Default to typing.Any.");
@@ -432,11 +440,12 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
             }
             pydanticImports.add("conlist");
             return String.format(Locale.ROOT, "conlist(%s%s)",
-                    getPydanticType(cp.items, typingImports, pydanticImports, datetimeImports, modelImports),
+                    getPydanticType(cp.items, typingImports, pydanticImports, datetimeImports, modelImports, classname),
                     constraints);
         } else if (cp.isMap) {
             typingImports.add("Dict");
-            return String.format(Locale.ROOT, "Dict[str, %s]", getPydanticType(cp.items, typingImports, pydanticImports, datetimeImports, modelImports));
+            return String.format(Locale.ROOT, "Dict[str, %s]",
+                    getPydanticType(cp.items, typingImports, pydanticImports, datetimeImports, modelImports, classname));
         } else if (cp.isString || cp.isBinary || cp.isByteArray) {
             if (cp.hasValidation) {
                 List<String> fieldCustomization = new ArrayList<>();
@@ -612,7 +621,7 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
                 CodegenMediaType cmt = contents.get(key);
                 // TODO process the first one only at the moment
                 if (cmt != null)
-                    return getPydanticType(cmt.getSchema(), typingImports, pydanticImports, datetimeImports, modelImports);
+                    return getPydanticType(cmt.getSchema(), typingImports, pydanticImports, datetimeImports, modelImports, classname);
             }
             throw new RuntimeException("Error! Failed to process getPydanticType when getting the content: " + cp);
         } else {
@@ -627,6 +636,8 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
      * @param typingImports typing imports
      * @param pydantic pydantic imports
      * @param datetimeImports datetime imports
+     * @param modelImports model imports
+     * @param classname class name
      * @return pydantic type
      *
      */
@@ -634,7 +645,8 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
                                    Set<String> typingImports,
                                    Set<String> pydanticImports,
                                    Set<String> datetimeImports,
-                                   Set<String> modelImports) {
+                                   Set<String> modelImports,
+                                   String classname) {
         if (cp == null) {
             // if codegen property (e.g. map/dict of undefined type) is null, default to string
             LOGGER.warn("Codegen property is null (e.g. map/dict of undefined type). Default to typing.Any.");
@@ -674,11 +686,11 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
             pydanticImports.add("conlist");
             typingImports.add("List"); // for return type
             return String.format(Locale.ROOT, "conlist(%s%s)",
-                    getPydanticType(cp.items, typingImports, pydanticImports, datetimeImports, modelImports),
+                    getPydanticType(cp.items, typingImports, pydanticImports, datetimeImports, modelImports, classname),
                     constraints);
         } else if (cp.isMap) {
             typingImports.add("Dict");
-            return String.format(Locale.ROOT, "Dict[str, %s]", getPydanticType(cp.items, typingImports, pydanticImports, datetimeImports, modelImports));
+            return String.format(Locale.ROOT, "Dict[str, %s]", getPydanticType(cp.items, typingImports, pydanticImports, datetimeImports, modelImports, classname));
         } else if (cp.isString) {
             if (cp.hasValidation) {
                 List<String> fieldCustomization = new ArrayList<>();
@@ -846,10 +858,24 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
             typingImports.add("Any");
             return "Dict[str, Any]";
         } else if (!cp.isPrimitiveType || cp.isModel) { // model
-            if (!cp.isCircularReference) {
-                // skip import if it's a circular reference
+            // skip import if it's a circular reference
+            if (classname == null) {
+                // for parameter model, import directly
                 hasModelsToImport = true;
                 modelImports.add(cp.dataType);
+            } else {
+                if (circularImports.containsKey(cp.dataType)) {
+                    if (circularImports.get(cp.dataType).contains(classname)) {
+                        // cp.dataType import map of set contains this model (classname), don't import
+                        LOGGER.debug("Skipped importing {} in {} due to circular import.", cp.dataType, classname);
+                    } else {
+                        // not circular import, so ok to import it
+                        hasModelsToImport = true;
+                        modelImports.add(cp.dataType);
+                    }
+                } else {
+                    LOGGER.error("Failed to look up {} from the imports (map of set) of models.", cp.dataType);
+                }
             }
             return cp.dataType;
         } else {
@@ -871,7 +897,7 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
 
             List<CodegenParameter> params = operation.allParams;
             for (CodegenParameter param : params) {
-                String typing = getPydanticType(param, typingImports, pydanticImports, datetimeImports, modelImports);
+                String typing = getPydanticType(param, typingImports, pydanticImports, datetimeImports, modelImports, null);
                 List<String> fields = new ArrayList<>();
                 String firstField = "";
 
@@ -923,7 +949,7 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
             // update typing import for operation return type
             if (!StringUtils.isEmpty(operation.returnType)) {
                 String typing = getPydanticType(operation.returnProperty, typingImports,
-                        new TreeSet<>() /* skip pydantic import for return type */, datetimeImports, modelImports);
+                        new TreeSet<>() /* skip pydantic import for return type */, datetimeImports, modelImports, null);
             }
 
         }
@@ -983,6 +1009,18 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
     @Override
     public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs) {
         final Map<String, ModelsMap> processed = super.postProcessAllModels(objs);
+
+        for (Map.Entry<String, ModelsMap> entry : objs.entrySet()) {
+            // create hash map of codegen model
+            CodegenModel cm = ModelUtils.getModelByName(entry.getKey(), objs);
+            codegenModelMap.put(cm.classname, ModelUtils.getModelByName(entry.getKey(), objs));
+        }
+
+        // create circular import
+        for (String m : codegenModelMap.keySet()) {
+            createImportMapOfSet(m, codegenModelMap);
+        }
+
         for (Map.Entry<String, ModelsMap> entry : processed.entrySet()) {
             entry.setValue(postProcessModelsMap(entry.getValue()));
         }
@@ -990,6 +1028,99 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
         return processed;
     }
 
+    /**
+     * Update circularImports with the model name (key) and its imports gathered recursively
+     *
+     * @param modelName       model name
+     * @param codegenModelMap a map of CodegenModel
+     */
+    void createImportMapOfSet(String modelName, Map<String, CodegenModel> codegenModelMap) {
+        HashSet<String> imports = new HashSet<>();
+        circularImports.put(modelName, imports);
+
+        CodegenModel cm = codegenModelMap.get(modelName);
+
+        if (cm == null) {
+            LOGGER.warn("Failed to lookup model in createImportMapOfSet: " + modelName);
+            return;
+        }
+
+        List<CodegenProperty> codegenProperties = null;
+        if (cm.oneOf != null && !cm.oneOf.isEmpty()) { // oneOf
+            codegenProperties = cm.getComposedSchemas().getOneOf();
+        } else if (cm.anyOf != null && !cm.anyOf.isEmpty()) { // anyOF
+            codegenProperties = cm.getComposedSchemas().getAnyOf();
+        } else { // typical model
+            codegenProperties = cm.vars;
+        }
+
+        for (CodegenProperty cp : codegenProperties) {
+            String modelNameFromDataType = getModelNameFromDataType(cp);
+            if (modelNameFromDataType != null) { // model
+                imports.add(modelNameFromDataType); // update import
+                // go through properties or sub-schemas of the model recursively to identify more (model) import if any
+                updateImportsFromCodegenModel(modelNameFromDataType, codegenModelMap.get(modelNameFromDataType), imports);
+            }
+        }
+    }
+
+    /**
+     * Update set of imports from codegen model recursivly
+     *
+     * @param modelName model name
+     * @param cm        codegen model
+     * @param imports   set of imports
+     */
+    public void updateImportsFromCodegenModel(String modelName, CodegenModel cm, Set<String> imports) {
+        if (cm == null) {
+            LOGGER.warn("Failed to lookup model in createImportMapOfSet " + modelName);
+            return;
+        }
+
+        List<CodegenProperty> codegenProperties = null;
+        if (cm.oneOf != null && !cm.oneOf.isEmpty()) { // oneOfValidationError
+            codegenProperties = cm.getComposedSchemas().getOneOf();
+        } else if (cm.anyOf != null && !cm.anyOf.isEmpty()) { // anyOF
+            codegenProperties = cm.getComposedSchemas().getAnyOf();
+        } else { // typical model
+            codegenProperties = cm.vars;
+        }
+
+        for (CodegenProperty cp : codegenProperties) {
+            String modelNameFromDataType = getModelNameFromDataType(cp);
+            if (modelNameFromDataType != null) { // model
+                if (modelName.equals(modelNameFromDataType)) { // self referencing
+                    continue;
+                } else if (imports.contains(modelNameFromDataType)) { // circular import
+                    continue;
+                } else {
+                    imports.add(modelNameFromDataType); // update import
+                    // go through properties of the model recursively to identify more (model) import if any
+                    updateImportsFromCodegenModel(modelNameFromDataType, codegenModelMap.get(modelNameFromDataType), imports);
+                }
+            }
+        }
+    }
+
+    /**
+     * Returns the model name (if any) from data type of codegen property.
+     * Returns null if it's not a model.
+     *
+     * @param cp Codegen property
+     * @return model name
+     */
+    private String getModelNameFromDataType(CodegenProperty cp) {
+        if (cp.isArray) {
+            return getModelNameFromDataType(cp.items);
+        } else if (cp.isMap) {
+            return getModelNameFromDataType(cp.items);
+        } else if (!cp.isPrimitiveType || cp.isModel) {
+            return cp.dataType;
+        } else {
+            return null;
+        }
+    }
+
     private ModelsMap postProcessModelsMap(ModelsMap objs) {
         // process enum in models
         objs = postProcessModelsEnum(objs);
@@ -1044,7 +1175,7 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
 
             //loop through properties/schemas to set up typing, pydantic
             for (CodegenProperty cp : codegenProperties) {
-                String typing = getPydanticType(cp, typingImports, pydanticImports, datetimeImports, modelImports);
+                String typing = getPydanticType(cp, typingImports, pydanticImports, datetimeImports, modelImports, model.classname);
                 List<String> fields = new ArrayList<>();
                 String firstField = "";
 
diff --git a/modules/openapi-generator/src/test/resources/3_0/python/petstore-with-fake-endpoints-models-for-testing.yaml b/modules/openapi-generator/src/test/resources/3_0/python/petstore-with-fake-endpoints-models-for-testing.yaml
index c8e80e14301..9dedcf30521 100644
--- a/modules/openapi-generator/src/test/resources/3_0/python/petstore-with-fake-endpoints-models-for-testing.yaml
+++ b/modules/openapi-generator/src/test/resources/3_0/python/petstore-with-fake-endpoints-models-for-testing.yaml
@@ -2126,3 +2126,24 @@ components:
       properties:
         optionalDict:
           $ref: "#/components/schemas/DictWithAdditionalProperties"
+    Circular-Reference-Model:
+      type: object
+      properties:
+        size:
+          type: integer
+        nested:
+          $ref: '#/components/schemas/FirstRef'
+    FirstRef:
+      type: object
+      properties:
+        category:
+          type: string
+        self_ref:
+          $ref: '#/components/schemas/SecondRef'
+    SecondRef:
+      type: object
+      properties:
+        category:
+          type: string
+        circular_ref:
+          $ref: '#/components/schemas/Circular-Reference-Model'
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/.openapi-generator/FILES b/samples/openapi3/client/petstore/python-nextgen-aiohttp/.openapi-generator/FILES
index 5d9cf72b28b..970be2c4e66 100644
--- a/samples/openapi3/client/petstore/python-nextgen-aiohttp/.openapi-generator/FILES
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/.openapi-generator/FILES
@@ -18,6 +18,7 @@ docs/Capitalization.md
 docs/Cat.md
 docs/CatAllOf.md
 docs/Category.md
+docs/CircularReferenceModel.md
 docs/ClassModel.md
 docs/Client.md
 docs/Color.md
@@ -34,6 +35,7 @@ docs/FakeApi.md
 docs/FakeClassnameTags123Api.md
 docs/File.md
 docs/FileSchemaTestClass.md
+docs/FirstRef.md
 docs/Foo.md
 docs/FooGetDefaultResponse.md
 docs/FormatTest.md
@@ -61,6 +63,7 @@ docs/Pet.md
 docs/PetApi.md
 docs/Pig.md
 docs/ReadOnlyFirst.md
+docs/SecondRef.md
 docs/SelfReferenceModel.md
 docs/SingleRefType.md
 docs/SpecialCharacterEnum.md
@@ -99,6 +102,7 @@ petstore_api/models/capitalization.py
 petstore_api/models/cat.py
 petstore_api/models/cat_all_of.py
 petstore_api/models/category.py
+petstore_api/models/circular_reference_model.py
 petstore_api/models/class_model.py
 petstore_api/models/client.py
 petstore_api/models/color.py
@@ -112,6 +116,7 @@ petstore_api/models/enum_class.py
 petstore_api/models/enum_test.py
 petstore_api/models/file.py
 petstore_api/models/file_schema_test_class.py
+petstore_api/models/first_ref.py
 petstore_api/models/foo.py
 petstore_api/models/foo_get_default_response.py
 petstore_api/models/format_test.py
@@ -138,6 +143,7 @@ petstore_api/models/parent_with_optional_dict.py
 petstore_api/models/pet.py
 petstore_api/models/pig.py
 petstore_api/models/read_only_first.py
+petstore_api/models/second_ref.py
 petstore_api/models/self_reference_model.py
 petstore_api/models/single_ref_type.py
 petstore_api/models/special_character_enum.py
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/README.md b/samples/openapi3/client/petstore/python-nextgen-aiohttp/README.md
index 9a72457e234..e26d9f33e89 100644
--- a/samples/openapi3/client/petstore/python-nextgen-aiohttp/README.md
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/README.md
@@ -146,6 +146,7 @@ Class | Method | HTTP request | Description
  - [Cat](docs/Cat.md)
  - [CatAllOf](docs/CatAllOf.md)
  - [Category](docs/Category.md)
+ - [CircularReferenceModel](docs/CircularReferenceModel.md)
  - [ClassModel](docs/ClassModel.md)
  - [Client](docs/Client.md)
  - [Color](docs/Color.md)
@@ -159,6 +160,7 @@ Class | Method | HTTP request | Description
  - [EnumTest](docs/EnumTest.md)
  - [File](docs/File.md)
  - [FileSchemaTestClass](docs/FileSchemaTestClass.md)
+ - [FirstRef](docs/FirstRef.md)
  - [Foo](docs/Foo.md)
  - [FooGetDefaultResponse](docs/FooGetDefaultResponse.md)
  - [FormatTest](docs/FormatTest.md)
@@ -185,6 +187,7 @@ Class | Method | HTTP request | Description
  - [Pet](docs/Pet.md)
  - [Pig](docs/Pig.md)
  - [ReadOnlyFirst](docs/ReadOnlyFirst.md)
+ - [SecondRef](docs/SecondRef.md)
  - [SelfReferenceModel](docs/SelfReferenceModel.md)
  - [SingleRefType](docs/SingleRefType.md)
  - [SpecialCharacterEnum](docs/SpecialCharacterEnum.md)
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/CircularReferenceModel.md b/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/CircularReferenceModel.md
new file mode 100644
index 00000000000..d5e97934d2b
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/CircularReferenceModel.md
@@ -0,0 +1,29 @@
+# CircularReferenceModel
+
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**size** | **int** |  | [optional] 
+**nested** | [**FirstRef**](FirstRef.md) |  | [optional] 
+
+## Example
+
+```python
+from petstore_api.models.circular_reference_model import CircularReferenceModel
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of CircularReferenceModel from a JSON string
+circular_reference_model_instance = CircularReferenceModel.from_json(json)
+# print the JSON string representation of the object
+print CircularReferenceModel.to_json()
+
+# convert the object into a dict
+circular_reference_model_dict = circular_reference_model_instance.to_dict()
+# create an instance of CircularReferenceModel from a dict
+circular_reference_model_form_dict = circular_reference_model.from_dict(circular_reference_model_dict)
+```
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/FirstRef.md b/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/FirstRef.md
new file mode 100644
index 00000000000..b5e7ab766b4
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/FirstRef.md
@@ -0,0 +1,29 @@
+# FirstRef
+
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**category** | **str** |  | [optional] 
+**self_ref** | [**SecondRef**](SecondRef.md) |  | [optional] 
+
+## Example
+
+```python
+from petstore_api.models.first_ref import FirstRef
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of FirstRef from a JSON string
+first_ref_instance = FirstRef.from_json(json)
+# print the JSON string representation of the object
+print FirstRef.to_json()
+
+# convert the object into a dict
+first_ref_dict = first_ref_instance.to_dict()
+# create an instance of FirstRef from a dict
+first_ref_form_dict = first_ref.from_dict(first_ref_dict)
+```
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/SecondRef.md b/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/SecondRef.md
new file mode 100644
index 00000000000..e6fb1e2d4f7
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/docs/SecondRef.md
@@ -0,0 +1,29 @@
+# SecondRef
+
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**category** | **str** |  | [optional] 
+**circular_ref** | [**CircularReferenceModel**](CircularReferenceModel.md) |  | [optional] 
+
+## Example
+
+```python
+from petstore_api.models.second_ref import SecondRef
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of SecondRef from a JSON string
+second_ref_instance = SecondRef.from_json(json)
+# print the JSON string representation of the object
+print SecondRef.to_json()
+
+# convert the object into a dict
+second_ref_dict = second_ref_instance.to_dict()
+# create an instance of SecondRef from a dict
+second_ref_form_dict = second_ref.from_dict(second_ref_dict)
+```
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/__init__.py b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/__init__.py
index 31cf58fec33..417db16491d 100644
--- a/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/__init__.py
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/__init__.py
@@ -49,6 +49,7 @@ from petstore_api.models.capitalization import Capitalization
 from petstore_api.models.cat import Cat
 from petstore_api.models.cat_all_of import CatAllOf
 from petstore_api.models.category import Category
+from petstore_api.models.circular_reference_model import CircularReferenceModel
 from petstore_api.models.class_model import ClassModel
 from petstore_api.models.client import Client
 from petstore_api.models.color import Color
@@ -62,6 +63,7 @@ from petstore_api.models.enum_class import EnumClass
 from petstore_api.models.enum_test import EnumTest
 from petstore_api.models.file import File
 from petstore_api.models.file_schema_test_class import FileSchemaTestClass
+from petstore_api.models.first_ref import FirstRef
 from petstore_api.models.foo import Foo
 from petstore_api.models.foo_get_default_response import FooGetDefaultResponse
 from petstore_api.models.format_test import FormatTest
@@ -88,6 +90,7 @@ from petstore_api.models.parent_with_optional_dict import ParentWithOptionalDict
 from petstore_api.models.pet import Pet
 from petstore_api.models.pig import Pig
 from petstore_api.models.read_only_first import ReadOnlyFirst
+from petstore_api.models.second_ref import SecondRef
 from petstore_api.models.self_reference_model import SelfReferenceModel
 from petstore_api.models.single_ref_type import SingleRefType
 from petstore_api.models.special_character_enum import SpecialCharacterEnum
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/__init__.py b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/__init__.py
index b6cd78aa71c..212f2096311 100644
--- a/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/__init__.py
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/__init__.py
@@ -28,6 +28,7 @@ from petstore_api.models.capitalization import Capitalization
 from petstore_api.models.cat import Cat
 from petstore_api.models.cat_all_of import CatAllOf
 from petstore_api.models.category import Category
+from petstore_api.models.circular_reference_model import CircularReferenceModel
 from petstore_api.models.class_model import ClassModel
 from petstore_api.models.client import Client
 from petstore_api.models.color import Color
@@ -41,6 +42,7 @@ from petstore_api.models.enum_class import EnumClass
 from petstore_api.models.enum_test import EnumTest
 from petstore_api.models.file import File
 from petstore_api.models.file_schema_test_class import FileSchemaTestClass
+from petstore_api.models.first_ref import FirstRef
 from petstore_api.models.foo import Foo
 from petstore_api.models.foo_get_default_response import FooGetDefaultResponse
 from petstore_api.models.format_test import FormatTest
@@ -67,6 +69,7 @@ from petstore_api.models.parent_with_optional_dict import ParentWithOptionalDict
 from petstore_api.models.pet import Pet
 from petstore_api.models.pig import Pig
 from petstore_api.models.read_only_first import ReadOnlyFirst
+from petstore_api.models.second_ref import SecondRef
 from petstore_api.models.self_reference_model import SelfReferenceModel
 from petstore_api.models.single_ref_type import SingleRefType
 from petstore_api.models.special_character_enum import SpecialCharacterEnum
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/circular_reference_model.py b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/circular_reference_model.py
new file mode 100644
index 00000000000..3a03dad4ddd
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/circular_reference_model.py
@@ -0,0 +1,75 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import annotations
+from inspect import getfullargspec
+import pprint
+import re  # noqa: F401
+import json
+
+
+from typing import Optional
+from pydantic import BaseModel, StrictInt
+
+class CircularReferenceModel(BaseModel):
+    """
+    CircularReferenceModel
+    """
+    size: Optional[StrictInt] = None
+    nested: Optional[FirstRef] = None
+    __properties = ["size", "nested"]
+
+    class Config:
+        allow_population_by_field_name = True
+        validate_assignment = True
+
+    def to_str(self) -> str:
+        """Returns the string representation of the model using alias"""
+        return pprint.pformat(self.dict(by_alias=True))
+
+    def to_json(self) -> str:
+        """Returns the JSON representation of the model using alias"""
+        return json.dumps(self.to_dict())
+
+    @classmethod
+    def from_json(cls, json_str: str) -> CircularReferenceModel:
+        """Create an instance of CircularReferenceModel from a JSON string"""
+        return cls.from_dict(json.loads(json_str))
+
+    def to_dict(self):
+        """Returns the dictionary representation of the model using alias"""
+        _dict = self.dict(by_alias=True,
+                          exclude={
+                          },
+                          exclude_none=True)
+        # override the default output from pydantic by calling `to_dict()` of nested
+        if self.nested:
+            _dict['nested'] = self.nested.to_dict()
+        return _dict
+
+    @classmethod
+    def from_dict(cls, obj: dict) -> CircularReferenceModel:
+        """Create an instance of CircularReferenceModel from a dict"""
+        if obj is None:
+            return None
+
+        if type(obj) is not dict:
+            return CircularReferenceModel.parse_obj(obj)
+
+        _obj = CircularReferenceModel.parse_obj({
+            "size": obj.get("size"),
+            "nested": FirstRef.from_dict(obj.get("nested")) if obj.get("nested") is not None else None
+        })
+        return _obj
+
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/first_ref.py b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/first_ref.py
new file mode 100644
index 00000000000..0856f9b0daf
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/first_ref.py
@@ -0,0 +1,75 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import annotations
+from inspect import getfullargspec
+import pprint
+import re  # noqa: F401
+import json
+
+
+from typing import Optional
+from pydantic import BaseModel, StrictStr
+
+class FirstRef(BaseModel):
+    """
+    FirstRef
+    """
+    category: Optional[StrictStr] = None
+    self_ref: Optional[SecondRef] = None
+    __properties = ["category", "self_ref"]
+
+    class Config:
+        allow_population_by_field_name = True
+        validate_assignment = True
+
+    def to_str(self) -> str:
+        """Returns the string representation of the model using alias"""
+        return pprint.pformat(self.dict(by_alias=True))
+
+    def to_json(self) -> str:
+        """Returns the JSON representation of the model using alias"""
+        return json.dumps(self.to_dict())
+
+    @classmethod
+    def from_json(cls, json_str: str) -> FirstRef:
+        """Create an instance of FirstRef from a JSON string"""
+        return cls.from_dict(json.loads(json_str))
+
+    def to_dict(self):
+        """Returns the dictionary representation of the model using alias"""
+        _dict = self.dict(by_alias=True,
+                          exclude={
+                          },
+                          exclude_none=True)
+        # override the default output from pydantic by calling `to_dict()` of self_ref
+        if self.self_ref:
+            _dict['self_ref'] = self.self_ref.to_dict()
+        return _dict
+
+    @classmethod
+    def from_dict(cls, obj: dict) -> FirstRef:
+        """Create an instance of FirstRef from a dict"""
+        if obj is None:
+            return None
+
+        if type(obj) is not dict:
+            return FirstRef.parse_obj(obj)
+
+        _obj = FirstRef.parse_obj({
+            "category": obj.get("category"),
+            "self_ref": SecondRef.from_dict(obj.get("self_ref")) if obj.get("self_ref") is not None else None
+        })
+        return _obj
+
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/second_ref.py b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/second_ref.py
new file mode 100644
index 00000000000..f00e2756920
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/second_ref.py
@@ -0,0 +1,75 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import annotations
+from inspect import getfullargspec
+import pprint
+import re  # noqa: F401
+import json
+
+
+from typing import Optional
+from pydantic import BaseModel, StrictStr
+
+class SecondRef(BaseModel):
+    """
+    SecondRef
+    """
+    category: Optional[StrictStr] = None
+    circular_ref: Optional[CircularReferenceModel] = None
+    __properties = ["category", "circular_ref"]
+
+    class Config:
+        allow_population_by_field_name = True
+        validate_assignment = True
+
+    def to_str(self) -> str:
+        """Returns the string representation of the model using alias"""
+        return pprint.pformat(self.dict(by_alias=True))
+
+    def to_json(self) -> str:
+        """Returns the JSON representation of the model using alias"""
+        return json.dumps(self.to_dict())
+
+    @classmethod
+    def from_json(cls, json_str: str) -> SecondRef:
+        """Create an instance of SecondRef from a JSON string"""
+        return cls.from_dict(json.loads(json_str))
+
+    def to_dict(self):
+        """Returns the dictionary representation of the model using alias"""
+        _dict = self.dict(by_alias=True,
+                          exclude={
+                          },
+                          exclude_none=True)
+        # override the default output from pydantic by calling `to_dict()` of circular_ref
+        if self.circular_ref:
+            _dict['circular_ref'] = self.circular_ref.to_dict()
+        return _dict
+
+    @classmethod
+    def from_dict(cls, obj: dict) -> SecondRef:
+        """Create an instance of SecondRef from a dict"""
+        if obj is None:
+            return None
+
+        if type(obj) is not dict:
+            return SecondRef.parse_obj(obj)
+
+        _obj = SecondRef.parse_obj({
+            "category": obj.get("category"),
+            "circular_ref": CircularReferenceModel.from_dict(obj.get("circular_ref")) if obj.get("circular_ref") is not None else None
+        })
+        return _obj
+
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_circular_reference_model.py b/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_circular_reference_model.py
new file mode 100644
index 00000000000..f734d3fc0ff
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_circular_reference_model.py
@@ -0,0 +1,64 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import absolute_import
+
+import unittest
+import datetime
+
+import petstore_api
+from petstore_api.models.circular_reference_model import CircularReferenceModel  # noqa: E501
+from petstore_api.rest import ApiException
+
+class TestCircularReferenceModel(unittest.TestCase):
+    """CircularReferenceModel unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def make_instance(self, include_optional):
+        """Test CircularReferenceModel
+            include_option is a boolean, when False only required
+            params are included, when True both required and
+            optional params are included """
+        # uncomment below to create an instance of `CircularReferenceModel`
+        """
+        model = petstore_api.models.circular_reference_model.CircularReferenceModel()  # noqa: E501
+        if include_optional :
+            return CircularReferenceModel(
+                size = 56, 
+                nested = petstore_api.models.first_ref.FirstRef(
+                    category = '', 
+                    self_ref = petstore_api.models.second_ref.SecondRef(
+                        category = '', 
+                        circular_ref = petstore_api.models.circular_reference_model.Circular-Reference-Model(
+                            size = 56, 
+                            nested = petstore_api.models.first_ref.FirstRef(
+                                category = '', ), ), ), )
+            )
+        else :
+            return CircularReferenceModel(
+        )
+        """
+
+    def testCircularReferenceModel(self):
+        """Test CircularReferenceModel"""
+        # inst_req_only = self.make_instance(include_optional=False)
+        # inst_req_and_optional = self.make_instance(include_optional=True)
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_first_ref.py b/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_first_ref.py
new file mode 100644
index 00000000000..bcec1c0334b
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_first_ref.py
@@ -0,0 +1,62 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import absolute_import
+
+import unittest
+import datetime
+
+import petstore_api
+from petstore_api.models.first_ref import FirstRef  # noqa: E501
+from petstore_api.rest import ApiException
+
+class TestFirstRef(unittest.TestCase):
+    """FirstRef unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def make_instance(self, include_optional):
+        """Test FirstRef
+            include_option is a boolean, when False only required
+            params are included, when True both required and
+            optional params are included """
+        # uncomment below to create an instance of `FirstRef`
+        """
+        model = petstore_api.models.first_ref.FirstRef()  # noqa: E501
+        if include_optional :
+            return FirstRef(
+                category = '', 
+                self_ref = petstore_api.models.second_ref.SecondRef(
+                    category = '', 
+                    circular_ref = petstore_api.models.circular_reference_model.Circular-Reference-Model(
+                        size = 56, 
+                        nested = petstore_api.models.first_ref.FirstRef(
+                            category = '', ), ), )
+            )
+        else :
+            return FirstRef(
+        )
+        """
+
+    def testFirstRef(self):
+        """Test FirstRef"""
+        # inst_req_only = self.make_instance(include_optional=False)
+        # inst_req_and_optional = self.make_instance(include_optional=True)
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_second_ref.py b/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_second_ref.py
new file mode 100644
index 00000000000..782892fd4e1
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen-aiohttp/test/test_second_ref.py
@@ -0,0 +1,62 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import absolute_import
+
+import unittest
+import datetime
+
+import petstore_api
+from petstore_api.models.second_ref import SecondRef  # noqa: E501
+from petstore_api.rest import ApiException
+
+class TestSecondRef(unittest.TestCase):
+    """SecondRef unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def make_instance(self, include_optional):
+        """Test SecondRef
+            include_option is a boolean, when False only required
+            params are included, when True both required and
+            optional params are included """
+        # uncomment below to create an instance of `SecondRef`
+        """
+        model = petstore_api.models.second_ref.SecondRef()  # noqa: E501
+        if include_optional :
+            return SecondRef(
+                category = '', 
+                circular_ref = petstore_api.models.circular_reference_model.Circular-Reference-Model(
+                    size = 56, 
+                    nested = petstore_api.models.first_ref.FirstRef(
+                        category = '', 
+                        self_ref = petstore_api.models.second_ref.SecondRef(
+                            category = '', ), ), )
+            )
+        else :
+            return SecondRef(
+        )
+        """
+
+    def testSecondRef(self):
+        """Test SecondRef"""
+        # inst_req_only = self.make_instance(include_optional=False)
+        # inst_req_and_optional = self.make_instance(include_optional=True)
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/samples/openapi3/client/petstore/python-nextgen/.openapi-generator/FILES b/samples/openapi3/client/petstore/python-nextgen/.openapi-generator/FILES
index c84577aa151..1c063f5f802 100755
--- a/samples/openapi3/client/petstore/python-nextgen/.openapi-generator/FILES
+++ b/samples/openapi3/client/petstore/python-nextgen/.openapi-generator/FILES
@@ -18,6 +18,7 @@ docs/Capitalization.md
 docs/Cat.md
 docs/CatAllOf.md
 docs/Category.md
+docs/CircularReferenceModel.md
 docs/ClassModel.md
 docs/Client.md
 docs/Color.md
@@ -34,6 +35,7 @@ docs/FakeApi.md
 docs/FakeClassnameTags123Api.md
 docs/File.md
 docs/FileSchemaTestClass.md
+docs/FirstRef.md
 docs/Foo.md
 docs/FooGetDefaultResponse.md
 docs/FormatTest.md
@@ -61,6 +63,7 @@ docs/Pet.md
 docs/PetApi.md
 docs/Pig.md
 docs/ReadOnlyFirst.md
+docs/SecondRef.md
 docs/SelfReferenceModel.md
 docs/SingleRefType.md
 docs/SpecialCharacterEnum.md
@@ -99,6 +102,7 @@ petstore_api/models/capitalization.py
 petstore_api/models/cat.py
 petstore_api/models/cat_all_of.py
 petstore_api/models/category.py
+petstore_api/models/circular_reference_model.py
 petstore_api/models/class_model.py
 petstore_api/models/client.py
 petstore_api/models/color.py
@@ -112,6 +116,7 @@ petstore_api/models/enum_class.py
 petstore_api/models/enum_test.py
 petstore_api/models/file.py
 petstore_api/models/file_schema_test_class.py
+petstore_api/models/first_ref.py
 petstore_api/models/foo.py
 petstore_api/models/foo_get_default_response.py
 petstore_api/models/format_test.py
@@ -138,6 +143,7 @@ petstore_api/models/parent_with_optional_dict.py
 petstore_api/models/pet.py
 petstore_api/models/pig.py
 petstore_api/models/read_only_first.py
+petstore_api/models/second_ref.py
 petstore_api/models/self_reference_model.py
 petstore_api/models/single_ref_type.py
 petstore_api/models/special_character_enum.py
diff --git a/samples/openapi3/client/petstore/python-nextgen/README.md b/samples/openapi3/client/petstore/python-nextgen/README.md
index e64a6743b26..a7b98f0887e 100755
--- a/samples/openapi3/client/petstore/python-nextgen/README.md
+++ b/samples/openapi3/client/petstore/python-nextgen/README.md
@@ -146,6 +146,7 @@ Class | Method | HTTP request | Description
  - [Cat](docs/Cat.md)
  - [CatAllOf](docs/CatAllOf.md)
  - [Category](docs/Category.md)
+ - [CircularReferenceModel](docs/CircularReferenceModel.md)
  - [ClassModel](docs/ClassModel.md)
  - [Client](docs/Client.md)
  - [Color](docs/Color.md)
@@ -159,6 +160,7 @@ Class | Method | HTTP request | Description
  - [EnumTest](docs/EnumTest.md)
  - [File](docs/File.md)
  - [FileSchemaTestClass](docs/FileSchemaTestClass.md)
+ - [FirstRef](docs/FirstRef.md)
  - [Foo](docs/Foo.md)
  - [FooGetDefaultResponse](docs/FooGetDefaultResponse.md)
  - [FormatTest](docs/FormatTest.md)
@@ -185,6 +187,7 @@ Class | Method | HTTP request | Description
  - [Pet](docs/Pet.md)
  - [Pig](docs/Pig.md)
  - [ReadOnlyFirst](docs/ReadOnlyFirst.md)
+ - [SecondRef](docs/SecondRef.md)
  - [SelfReferenceModel](docs/SelfReferenceModel.md)
  - [SingleRefType](docs/SingleRefType.md)
  - [SpecialCharacterEnum](docs/SpecialCharacterEnum.md)
diff --git a/samples/openapi3/client/petstore/python-nextgen/docs/CircularReferenceModel.md b/samples/openapi3/client/petstore/python-nextgen/docs/CircularReferenceModel.md
new file mode 100644
index 00000000000..d5e97934d2b
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/docs/CircularReferenceModel.md
@@ -0,0 +1,29 @@
+# CircularReferenceModel
+
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**size** | **int** |  | [optional] 
+**nested** | [**FirstRef**](FirstRef.md) |  | [optional] 
+
+## Example
+
+```python
+from petstore_api.models.circular_reference_model import CircularReferenceModel
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of CircularReferenceModel from a JSON string
+circular_reference_model_instance = CircularReferenceModel.from_json(json)
+# print the JSON string representation of the object
+print CircularReferenceModel.to_json()
+
+# convert the object into a dict
+circular_reference_model_dict = circular_reference_model_instance.to_dict()
+# create an instance of CircularReferenceModel from a dict
+circular_reference_model_form_dict = circular_reference_model.from_dict(circular_reference_model_dict)
+```
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/openapi3/client/petstore/python-nextgen/docs/FirstRef.md b/samples/openapi3/client/petstore/python-nextgen/docs/FirstRef.md
new file mode 100644
index 00000000000..b5e7ab766b4
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/docs/FirstRef.md
@@ -0,0 +1,29 @@
+# FirstRef
+
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**category** | **str** |  | [optional] 
+**self_ref** | [**SecondRef**](SecondRef.md) |  | [optional] 
+
+## Example
+
+```python
+from petstore_api.models.first_ref import FirstRef
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of FirstRef from a JSON string
+first_ref_instance = FirstRef.from_json(json)
+# print the JSON string representation of the object
+print FirstRef.to_json()
+
+# convert the object into a dict
+first_ref_dict = first_ref_instance.to_dict()
+# create an instance of FirstRef from a dict
+first_ref_form_dict = first_ref.from_dict(first_ref_dict)
+```
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/openapi3/client/petstore/python-nextgen/docs/SecondRef.md b/samples/openapi3/client/petstore/python-nextgen/docs/SecondRef.md
new file mode 100644
index 00000000000..e6fb1e2d4f7
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/docs/SecondRef.md
@@ -0,0 +1,29 @@
+# SecondRef
+
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**category** | **str** |  | [optional] 
+**circular_ref** | [**CircularReferenceModel**](CircularReferenceModel.md) |  | [optional] 
+
+## Example
+
+```python
+from petstore_api.models.second_ref import SecondRef
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of SecondRef from a JSON string
+second_ref_instance = SecondRef.from_json(json)
+# print the JSON string representation of the object
+print SecondRef.to_json()
+
+# convert the object into a dict
+second_ref_dict = second_ref_instance.to_dict()
+# create an instance of SecondRef from a dict
+second_ref_form_dict = second_ref.from_dict(second_ref_dict)
+```
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/openapi3/client/petstore/python-nextgen/petstore_api/__init__.py b/samples/openapi3/client/petstore/python-nextgen/petstore_api/__init__.py
index 31cf58fec33..417db16491d 100755
--- a/samples/openapi3/client/petstore/python-nextgen/petstore_api/__init__.py
+++ b/samples/openapi3/client/petstore/python-nextgen/petstore_api/__init__.py
@@ -49,6 +49,7 @@ from petstore_api.models.capitalization import Capitalization
 from petstore_api.models.cat import Cat
 from petstore_api.models.cat_all_of import CatAllOf
 from petstore_api.models.category import Category
+from petstore_api.models.circular_reference_model import CircularReferenceModel
 from petstore_api.models.class_model import ClassModel
 from petstore_api.models.client import Client
 from petstore_api.models.color import Color
@@ -62,6 +63,7 @@ from petstore_api.models.enum_class import EnumClass
 from petstore_api.models.enum_test import EnumTest
 from petstore_api.models.file import File
 from petstore_api.models.file_schema_test_class import FileSchemaTestClass
+from petstore_api.models.first_ref import FirstRef
 from petstore_api.models.foo import Foo
 from petstore_api.models.foo_get_default_response import FooGetDefaultResponse
 from petstore_api.models.format_test import FormatTest
@@ -88,6 +90,7 @@ from petstore_api.models.parent_with_optional_dict import ParentWithOptionalDict
 from petstore_api.models.pet import Pet
 from petstore_api.models.pig import Pig
 from petstore_api.models.read_only_first import ReadOnlyFirst
+from petstore_api.models.second_ref import SecondRef
 from petstore_api.models.self_reference_model import SelfReferenceModel
 from petstore_api.models.single_ref_type import SingleRefType
 from petstore_api.models.special_character_enum import SpecialCharacterEnum
diff --git a/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/__init__.py b/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/__init__.py
index b6cd78aa71c..212f2096311 100644
--- a/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/__init__.py
+++ b/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/__init__.py
@@ -28,6 +28,7 @@ from petstore_api.models.capitalization import Capitalization
 from petstore_api.models.cat import Cat
 from petstore_api.models.cat_all_of import CatAllOf
 from petstore_api.models.category import Category
+from petstore_api.models.circular_reference_model import CircularReferenceModel
 from petstore_api.models.class_model import ClassModel
 from petstore_api.models.client import Client
 from petstore_api.models.color import Color
@@ -41,6 +42,7 @@ from petstore_api.models.enum_class import EnumClass
 from petstore_api.models.enum_test import EnumTest
 from petstore_api.models.file import File
 from petstore_api.models.file_schema_test_class import FileSchemaTestClass
+from petstore_api.models.first_ref import FirstRef
 from petstore_api.models.foo import Foo
 from petstore_api.models.foo_get_default_response import FooGetDefaultResponse
 from petstore_api.models.format_test import FormatTest
@@ -67,6 +69,7 @@ from petstore_api.models.parent_with_optional_dict import ParentWithOptionalDict
 from petstore_api.models.pet import Pet
 from petstore_api.models.pig import Pig
 from petstore_api.models.read_only_first import ReadOnlyFirst
+from petstore_api.models.second_ref import SecondRef
 from petstore_api.models.self_reference_model import SelfReferenceModel
 from petstore_api.models.single_ref_type import SingleRefType
 from petstore_api.models.special_character_enum import SpecialCharacterEnum
diff --git a/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/circular_reference_model.py b/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/circular_reference_model.py
new file mode 100644
index 00000000000..eacb22736b3
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/circular_reference_model.py
@@ -0,0 +1,87 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import annotations
+from inspect import getfullargspec
+import pprint
+import re  # noqa: F401
+import json
+
+
+from typing import Optional
+from pydantic import BaseModel, StrictInt
+
+class CircularReferenceModel(BaseModel):
+    """
+    CircularReferenceModel
+    """
+    size: Optional[StrictInt] = None
+    nested: Optional[FirstRef] = None
+    additional_properties: Dict[str, Any] = {}
+    __properties = ["size", "nested"]
+
+    class Config:
+        allow_population_by_field_name = True
+        validate_assignment = True
+
+    def to_str(self) -> str:
+        """Returns the string representation of the model using alias"""
+        return pprint.pformat(self.dict(by_alias=True))
+
+    def to_json(self) -> str:
+        """Returns the JSON representation of the model using alias"""
+        return json.dumps(self.to_dict())
+
+    @classmethod
+    def from_json(cls, json_str: str) -> CircularReferenceModel:
+        """Create an instance of CircularReferenceModel from a JSON string"""
+        return cls.from_dict(json.loads(json_str))
+
+    def to_dict(self):
+        """Returns the dictionary representation of the model using alias"""
+        _dict = self.dict(by_alias=True,
+                          exclude={
+                            "additional_properties"
+                          },
+                          exclude_none=True)
+        # override the default output from pydantic by calling `to_dict()` of nested
+        if self.nested:
+            _dict['nested'] = self.nested.to_dict()
+        # puts key-value pairs in additional_properties in the top level
+        if self.additional_properties is not None:
+            for _key, _value in self.additional_properties.items():
+                _dict[_key] = _value
+
+        return _dict
+
+    @classmethod
+    def from_dict(cls, obj: dict) -> CircularReferenceModel:
+        """Create an instance of CircularReferenceModel from a dict"""
+        if obj is None:
+            return None
+
+        if type(obj) is not dict:
+            return CircularReferenceModel.parse_obj(obj)
+
+        _obj = CircularReferenceModel.parse_obj({
+            "size": obj.get("size"),
+            "nested": FirstRef.from_dict(obj.get("nested")) if obj.get("nested") is not None else None
+        })
+        # store additional fields in additional_properties
+        for _key in obj.keys():
+            if _key not in cls.__properties:
+                _obj.additional_properties[_key] = obj.get(_key)
+
+        return _obj
+
diff --git a/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/first_ref.py b/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/first_ref.py
new file mode 100644
index 00000000000..31ac2390677
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/first_ref.py
@@ -0,0 +1,87 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import annotations
+from inspect import getfullargspec
+import pprint
+import re  # noqa: F401
+import json
+
+
+from typing import Optional
+from pydantic import BaseModel, StrictStr
+
+class FirstRef(BaseModel):
+    """
+    FirstRef
+    """
+    category: Optional[StrictStr] = None
+    self_ref: Optional[SecondRef] = None
+    additional_properties: Dict[str, Any] = {}
+    __properties = ["category", "self_ref"]
+
+    class Config:
+        allow_population_by_field_name = True
+        validate_assignment = True
+
+    def to_str(self) -> str:
+        """Returns the string representation of the model using alias"""
+        return pprint.pformat(self.dict(by_alias=True))
+
+    def to_json(self) -> str:
+        """Returns the JSON representation of the model using alias"""
+        return json.dumps(self.to_dict())
+
+    @classmethod
+    def from_json(cls, json_str: str) -> FirstRef:
+        """Create an instance of FirstRef from a JSON string"""
+        return cls.from_dict(json.loads(json_str))
+
+    def to_dict(self):
+        """Returns the dictionary representation of the model using alias"""
+        _dict = self.dict(by_alias=True,
+                          exclude={
+                            "additional_properties"
+                          },
+                          exclude_none=True)
+        # override the default output from pydantic by calling `to_dict()` of self_ref
+        if self.self_ref:
+            _dict['self_ref'] = self.self_ref.to_dict()
+        # puts key-value pairs in additional_properties in the top level
+        if self.additional_properties is not None:
+            for _key, _value in self.additional_properties.items():
+                _dict[_key] = _value
+
+        return _dict
+
+    @classmethod
+    def from_dict(cls, obj: dict) -> FirstRef:
+        """Create an instance of FirstRef from a dict"""
+        if obj is None:
+            return None
+
+        if type(obj) is not dict:
+            return FirstRef.parse_obj(obj)
+
+        _obj = FirstRef.parse_obj({
+            "category": obj.get("category"),
+            "self_ref": SecondRef.from_dict(obj.get("self_ref")) if obj.get("self_ref") is not None else None
+        })
+        # store additional fields in additional_properties
+        for _key in obj.keys():
+            if _key not in cls.__properties:
+                _obj.additional_properties[_key] = obj.get(_key)
+
+        return _obj
+
diff --git a/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/second_ref.py b/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/second_ref.py
new file mode 100644
index 00000000000..228c8b24b92
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/petstore_api/models/second_ref.py
@@ -0,0 +1,87 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import annotations
+from inspect import getfullargspec
+import pprint
+import re  # noqa: F401
+import json
+
+
+from typing import Optional
+from pydantic import BaseModel, StrictStr
+
+class SecondRef(BaseModel):
+    """
+    SecondRef
+    """
+    category: Optional[StrictStr] = None
+    circular_ref: Optional[CircularReferenceModel] = None
+    additional_properties: Dict[str, Any] = {}
+    __properties = ["category", "circular_ref"]
+
+    class Config:
+        allow_population_by_field_name = True
+        validate_assignment = True
+
+    def to_str(self) -> str:
+        """Returns the string representation of the model using alias"""
+        return pprint.pformat(self.dict(by_alias=True))
+
+    def to_json(self) -> str:
+        """Returns the JSON representation of the model using alias"""
+        return json.dumps(self.to_dict())
+
+    @classmethod
+    def from_json(cls, json_str: str) -> SecondRef:
+        """Create an instance of SecondRef from a JSON string"""
+        return cls.from_dict(json.loads(json_str))
+
+    def to_dict(self):
+        """Returns the dictionary representation of the model using alias"""
+        _dict = self.dict(by_alias=True,
+                          exclude={
+                            "additional_properties"
+                          },
+                          exclude_none=True)
+        # override the default output from pydantic by calling `to_dict()` of circular_ref
+        if self.circular_ref:
+            _dict['circular_ref'] = self.circular_ref.to_dict()
+        # puts key-value pairs in additional_properties in the top level
+        if self.additional_properties is not None:
+            for _key, _value in self.additional_properties.items():
+                _dict[_key] = _value
+
+        return _dict
+
+    @classmethod
+    def from_dict(cls, obj: dict) -> SecondRef:
+        """Create an instance of SecondRef from a dict"""
+        if obj is None:
+            return None
+
+        if type(obj) is not dict:
+            return SecondRef.parse_obj(obj)
+
+        _obj = SecondRef.parse_obj({
+            "category": obj.get("category"),
+            "circular_ref": CircularReferenceModel.from_dict(obj.get("circular_ref")) if obj.get("circular_ref") is not None else None
+        })
+        # store additional fields in additional_properties
+        for _key in obj.keys():
+            if _key not in cls.__properties:
+                _obj.additional_properties[_key] = obj.get(_key)
+
+        return _obj
+
diff --git a/samples/openapi3/client/petstore/python-nextgen/test/test_circular_reference_model.py b/samples/openapi3/client/petstore/python-nextgen/test/test_circular_reference_model.py
new file mode 100644
index 00000000000..f734d3fc0ff
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/test/test_circular_reference_model.py
@@ -0,0 +1,64 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import absolute_import
+
+import unittest
+import datetime
+
+import petstore_api
+from petstore_api.models.circular_reference_model import CircularReferenceModel  # noqa: E501
+from petstore_api.rest import ApiException
+
+class TestCircularReferenceModel(unittest.TestCase):
+    """CircularReferenceModel unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def make_instance(self, include_optional):
+        """Test CircularReferenceModel
+            include_option is a boolean, when False only required
+            params are included, when True both required and
+            optional params are included """
+        # uncomment below to create an instance of `CircularReferenceModel`
+        """
+        model = petstore_api.models.circular_reference_model.CircularReferenceModel()  # noqa: E501
+        if include_optional :
+            return CircularReferenceModel(
+                size = 56, 
+                nested = petstore_api.models.first_ref.FirstRef(
+                    category = '', 
+                    self_ref = petstore_api.models.second_ref.SecondRef(
+                        category = '', 
+                        circular_ref = petstore_api.models.circular_reference_model.Circular-Reference-Model(
+                            size = 56, 
+                            nested = petstore_api.models.first_ref.FirstRef(
+                                category = '', ), ), ), )
+            )
+        else :
+            return CircularReferenceModel(
+        )
+        """
+
+    def testCircularReferenceModel(self):
+        """Test CircularReferenceModel"""
+        # inst_req_only = self.make_instance(include_optional=False)
+        # inst_req_and_optional = self.make_instance(include_optional=True)
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/samples/openapi3/client/petstore/python-nextgen/test/test_first_ref.py b/samples/openapi3/client/petstore/python-nextgen/test/test_first_ref.py
new file mode 100644
index 00000000000..bcec1c0334b
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/test/test_first_ref.py
@@ -0,0 +1,62 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import absolute_import
+
+import unittest
+import datetime
+
+import petstore_api
+from petstore_api.models.first_ref import FirstRef  # noqa: E501
+from petstore_api.rest import ApiException
+
+class TestFirstRef(unittest.TestCase):
+    """FirstRef unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def make_instance(self, include_optional):
+        """Test FirstRef
+            include_option is a boolean, when False only required
+            params are included, when True both required and
+            optional params are included """
+        # uncomment below to create an instance of `FirstRef`
+        """
+        model = petstore_api.models.first_ref.FirstRef()  # noqa: E501
+        if include_optional :
+            return FirstRef(
+                category = '', 
+                self_ref = petstore_api.models.second_ref.SecondRef(
+                    category = '', 
+                    circular_ref = petstore_api.models.circular_reference_model.Circular-Reference-Model(
+                        size = 56, 
+                        nested = petstore_api.models.first_ref.FirstRef(
+                            category = '', ), ), )
+            )
+        else :
+            return FirstRef(
+        )
+        """
+
+    def testFirstRef(self):
+        """Test FirstRef"""
+        # inst_req_only = self.make_instance(include_optional=False)
+        # inst_req_and_optional = self.make_instance(include_optional=True)
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/samples/openapi3/client/petstore/python-nextgen/test/test_second_ref.py b/samples/openapi3/client/petstore/python-nextgen/test/test_second_ref.py
new file mode 100644
index 00000000000..782892fd4e1
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-nextgen/test/test_second_ref.py
@@ -0,0 +1,62 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""
+
+
+from __future__ import absolute_import
+
+import unittest
+import datetime
+
+import petstore_api
+from petstore_api.models.second_ref import SecondRef  # noqa: E501
+from petstore_api.rest import ApiException
+
+class TestSecondRef(unittest.TestCase):
+    """SecondRef unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def make_instance(self, include_optional):
+        """Test SecondRef
+            include_option is a boolean, when False only required
+            params are included, when True both required and
+            optional params are included """
+        # uncomment below to create an instance of `SecondRef`
+        """
+        model = petstore_api.models.second_ref.SecondRef()  # noqa: E501
+        if include_optional :
+            return SecondRef(
+                category = '', 
+                circular_ref = petstore_api.models.circular_reference_model.Circular-Reference-Model(
+                    size = 56, 
+                    nested = petstore_api.models.first_ref.FirstRef(
+                        category = '', 
+                        self_ref = petstore_api.models.second_ref.SecondRef(
+                            category = '', ), ), )
+            )
+        else :
+            return SecondRef(
+        )
+        """
+
+    def testSecondRef(self):
+        """Test SecondRef"""
+        # inst_req_only = self.make_instance(include_optional=False)
+        # inst_req_and_optional = self.make_instance(include_optional=True)
+
+if __name__ == '__main__':
+    unittest.main()