[BUG] [python-legacy] Generated tests include invalid Python code when a member has the name of a keyword

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
  • No, but I have run it against v5.2.1 and verified that there are no relevant changes that would address it since then.
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When generating a schema with a message includes a sub-message with a reserved word (e.g. Wrapper has key whatever, which in turn has key dict), the generated test for Wrapper will include del = None in its whatever's parameter list.

openapi-generator version

v5.2.1

OpenAPI declaration file content or url

swagger: "2.0"
info:
  description: Bug
  title: Bug
  version: 0.0.0

produces:
- application/json
consumes:
- application/json

schemes:
- http
- https

basePath: /a-bug

definitions:
  Wrapper:
    type: object
    properties:
      whatever:
        type: object
        properties:
          del:
            type: boolean


paths:
  /test:
    get:
      description: i'm makeing a bug
      produces:
        - application/json
      consumes:
        - application/json
      responses:
        200:
          description: this is bad and wrong
          schema:
            $ref: "#/definitions/Wrapper"

Generation Details

java -jar openapi-generator-cli-5.2.1.jar generate -g python-legacy -o output-5.2.1-legacy -i bug.yaml

Steps to reproduce

1. Write above contents to bug.yaml.
2. Run:

   java -jar openapi-generator-cli-5.2.1.jar generate -g python-legacy -o output-5.2.1-legacy -i bug.yaml
   

Actual results (test/test_wrapper.py):

# coding: utf-8

"""
    Bug

    Bug  # noqa: E501

    The version of the OpenAPI document: 0.0.0
    Generated by: https://openapi-generator.tech
"""


from __future__ import absolute_import

import unittest
import datetime

import openapi_client
from openapi_client.models.wrapper import Wrapper  # noqa: E501
from openapi_client.rest import ApiException

class TestWrapper(unittest.TestCase):
    """Wrapper unit test stubs"""

    def setUp(self):
        pass

    def tearDown(self):
        pass

    def make_instance(self, include_optional):
        """Test Wrapper
            include_option is a boolean, when False only required
            params are included, when True both required and
            optional params are included """
        # model = openapi_client.models.wrapper.Wrapper()  # noqa: E501
        if include_optional :
            return Wrapper(
                whatever = openapi_client.models.wrapper_whatever.Wrapper_whatever(
                    del = True, )
            )
        else :
            return Wrapper(
        )

    def testWrapper(self):
        """Test Wrapper"""
        inst_req_only = self.make_instance(include_optional=False)
        inst_req_and_optional = self.make_instance(include_optional=True)

if __name__ == '__main__':
    unittest.main()

Expected results:

# coding: utf-8

"""
    Bug

    Bug  # noqa: E501

    The version of the OpenAPI document: 0.0.0
    Generated by: https://openapi-generator.tech
"""


from __future__ import absolute_import

import unittest
import datetime

import openapi_client
from openapi_client.models.wrapper import Wrapper  # noqa: E501
from openapi_client.rest import ApiException

class TestWrapper(unittest.TestCase):
    """Wrapper unit test stubs"""

    def setUp(self):
        pass

    def tearDown(self):
        pass

    def make_instance(self, include_optional):
        """Test Wrapper
            include_option is a boolean, when False only required
            params are included, when True both required and
            optional params are included """
        # model = openapi_client.models.wrapper.Wrapper()  # noqa: E501
        if include_optional :
            return Wrapper(
                whatever = openapi_client.models.wrapper_whatever.Wrapper_whatever(
####################################
                    _del = True, ) # UNDERSCORE ADDED HERE
####################################
            )
        else :
            return Wrapper(
        )

    def testWrapper(self):
        """Test Wrapper"""
        inst_req_only = self.make_instance(include_optional=False)
        inst_req_and_optional = self.make_instance(include_optional=True)

if __name__ == '__main__':
    unittest.main()

Suggest a fix

It seems that the examples here:
https://github.com/OpenAPITools/openapi-generator/blob/158649aff9a87b13b448880d7ca6a4ac35fadcc2/modules/openapi-generator/src/main/resources/python-legacy/model_test.mustache#L35
do not have their name parameters properly escaped.

Start with the referenced model_test.mustache template around line 35 and reproduce the issue using bug.yaml and the documented java -jar generation command. Check the generated test/test_wrapper.py for a reserved member name such as del; the work is done when the generated Python test uses the expected valid form instead of invalid syntax.