[python] Fix array of array of model's to_dict, from_dict (#16032)

* fix array of array of model's to_dict, from_dict

* update samples

samples/openapi3/client/petstore/python-aiohttp/test/test_array_of_array_of_model.py

@@ -0,0 +1,60 @@
+# 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.
+"""
+
+
+import unittest
+import datetime
+
+import petstore_api
+from petstore_api.models.array_of_array_of_model import ArrayOfArrayOfModel  # noqa: E501
+from petstore_api.rest import ApiException
+
+class TestArrayOfArrayOfModel(unittest.TestCase):
+    """ArrayOfArrayOfModel unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def make_instance(self, include_optional):
+        """Test ArrayOfArrayOfModel
+            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 `ArrayOfArrayOfModel`
+        """
+        model = petstore_api.models.array_of_array_of_model.ArrayOfArrayOfModel()  # noqa: E501
+        if include_optional :
+            return ArrayOfArrayOfModel(
+                another_property = [
+                    [
+                        petstore_api.models.tag.Tag(
+                            id = 56, 
+                            name = '', )
+                        ]
+                    ]
+            )
+        else :
+            return ArrayOfArrayOfModel(
+        )
+        """
+
+    def testArrayOfArrayOfModel(self):
+        """Test ArrayOfArrayOfModel"""
+        # inst_req_only = self.make_instance(include_optional=False)
+        # inst_req_and_optional = self.make_instance(include_optional=True)
+
+if __name__ == '__main__':
+    unittest.main()