[BUG][PYTHON] Reserved word escaping breaks python naming conventions

Description

The current method of escaping reserved words in variable names involves appending a leading underscore (_) to the variable name. Per PEP8 and community convention, variable names with a leading underscore are typically used to signify that the variable is internal and thus should not be considered part of the public interface of its containing scope. This is not only confusing due to convention, but also affects python's star (*) imports (from package import *) and commonly used tools (such as IPython) which rely on this convention to determine whether to include attributes for introspection and completion purposes.

openapi-generator version

4.0.0

OpenAPI declaration file content or url

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Status Check API
paths:
  /check:
    get:
      summary: Check Pass/Fail Status
      operationId: checkStatus
      responses:
        default:
          description: Status
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Status"
components:
  schemas:
    Status:
      required:
        - pass
      properties:
        pass:
          type: boolean

Command line used for generation

openapi-generator generate -i openapi.yaml -g python

Steps to reproduce

Give a property a name that collides with a python reserved word, such as pass in your declaration file and then generate a python package.

Suggest a fix

PEP8 recommends instead to append a trailing underscore, such that pass would become pass_.

Start with PythonClientCodegen.java at the linked reserved-word escaping method and reproduce the issue using the provided OpenAPI declaration and generate command. Check the generated Python package for the pass property; done means reserved names follow the requested naming convention without breaking generated access or imports.