fix #11958 [BUG] python generates wrong model name and model file name (#11959)

* fix #11958 [BUG] python generates wrong model name and model file name

Modify AbstractPythonCodegen.toModelName just like AbstractJavaCodegen.toModelName

* add unit test

* update samples and docs
by
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh

* fix AbstractPythonCodegen#toModelName logic, remove underscore

* update samples and docs
by
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh

samples/client/petstore/python-asyncio/docs/Model_200Response.md

@@ -0,0 +1,13 @@
+# Model_200Response
+
+Model for testing model name starting with number
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**name** | **int** |  | [optional] 
+**_class** | **str** |  | [optional] 
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+

samples/client/petstore/python-asyncio/docs/Model_Return.md

@@ -0,0 +1,12 @@
+# Model_Return
+
+Model for testing reserved words
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**_return** | **int** |  | [optional] 
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+

samples/client/petstore/python-asyncio/petstore_api/models/model_200_response.py

@@ -0,0 +1,157 @@
+# 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: https://openapi-generator.tech
+"""
+
+
+try:
+    from inspect import getfullargspec
+except ImportError:
+    from inspect import getargspec as getfullargspec
+import pprint
+import re  # noqa: F401
+import six
+
+from petstore_api.configuration import Configuration
+
+
+class Model_200Response(object):
+    """NOTE: This class is auto generated by OpenAPI Generator.
+    Ref: https://openapi-generator.tech
+
+    Do not edit the class manually.
+    """
+
+    """
+    Attributes:
+      openapi_types (dict): The key is attribute name
+                            and the value is attribute type.
+      attribute_map (dict): The key is attribute name
+                            and the value is json key in definition.
+    """
+    openapi_types = {
+        'name': 'int',
+        '_class': 'str'
+    }
+
+    attribute_map = {
+        'name': 'name',
+        '_class': 'class'
+    }
+
+    def __init__(self, name=None, _class=None, local_vars_configuration=None):  # noqa: E501
+        """Model_200Response - a model defined in OpenAPI"""  # noqa: E501
+        if local_vars_configuration is None:
+            local_vars_configuration = Configuration.get_default_copy()
+        self.local_vars_configuration = local_vars_configuration
+
+        self._name = None
+        self.__class = None
+        self.discriminator = None
+
+        if name is not None:
+            self.name = name
+        if _class is not None:
+            self._class = _class
+
+    @property
+    def name(self):
+        """Gets the name of this Model_200Response.  # noqa: E501
+
+
+        :return: The name of this Model_200Response.  # noqa: E501
+        :rtype: int
+        """
+        return self._name
+
+    @name.setter
+    def name(self, name):
+        """Sets the name of this Model_200Response.
+
+
+        :param name: The name of this Model_200Response.  # noqa: E501
+        :type name: int
+        """
+
+        self._name = name
+
+    @property
+    def _class(self):
+        """Gets the _class of this Model_200Response.  # noqa: E501
+
+
+        :return: The _class of this Model_200Response.  # noqa: E501
+        :rtype: str
+        """
+        return self.__class
+
+    @_class.setter
+    def _class(self, _class):
+        """Sets the _class of this Model_200Response.
+
+
+        :param _class: The _class of this Model_200Response.  # noqa: E501
+        :type _class: str
+        """
+
+        self.__class = _class
+
+    def to_dict(self, serialize=False):
+        """Returns the model properties as a dict"""
+        result = {}
+
+        def convert(x):
+            if hasattr(x, "to_dict"):
+                args = getfullargspec(x.to_dict).args
+                if len(args) == 1:
+                    return x.to_dict()
+                else:
+                    return x.to_dict(serialize)
+            else:
+                return x
+
+        for attr, _ in six.iteritems(self.openapi_types):
+            value = getattr(self, attr)
+            attr = self.attribute_map.get(attr, attr) if serialize else attr
+            if isinstance(value, list):
+                result[attr] = list(map(
+                    lambda x: convert(x),
+                    value
+                ))
+            elif isinstance(value, dict):
+                result[attr] = dict(map(
+                    lambda item: (item[0], convert(item[1])),
+                    value.items()
+                ))
+            else:
+                result[attr] = convert(value)
+
+        return result
+
+    def to_str(self):
+        """Returns the string representation of the model"""
+        return pprint.pformat(self.to_dict())
+
+    def __repr__(self):
+        """For `print` and `pprint`"""
+        return self.to_str()
+
+    def __eq__(self, other):
+        """Returns true if both objects are equal"""
+        if not isinstance(other, Model_200Response):
+            return False
+
+        return self.to_dict() == other.to_dict()
+
+    def __ne__(self, other):
+        """Returns true if both objects are not equal"""
+        if not isinstance(other, Model_200Response):
+            return True
+
+        return self.to_dict() != other.to_dict()

samples/client/petstore/python-asyncio/test/test_model_200_response.py

@@ -0,0 +1,52 @@
+# 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: https://openapi-generator.tech
+"""
+
+
+from __future__ import absolute_import
+
+import unittest
+import datetime
+
+import petstore_api
+from petstore_api.models.model_200_response import Model_200Response  # noqa: E501
+from petstore_api.rest import ApiException
+
+class TestModel_200Response(unittest.TestCase):
+    """Model_200Response unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def make_instance(self, include_optional):
+        """Test Model_200Response
+            include_option is a boolean, when False only required
+            params are included, when True both required and
+            optional params are included """
+        # model = petstore_api.models.model_200_response.Model_200Response()  # noqa: E501
+        if include_optional :
+            return Model_200Response(
+                name = 56, 
+                _class = ''
+            )
+        else :
+            return Model_200Response(
+        )
+
+    def testModel_200Response(self):
+        """Test Model_200Response"""
+        inst_req_only = self.make_instance(include_optional=False)
+        inst_req_and_optional = self.make_instance(include_optional=True)
+
+if __name__ == '__main__':
+    unittest.main()