[BUG] [PYTHON] Invalid code generated for polymorphism when name has double underscores

[YousefHaggy]

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?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

The template code for python imports using classVarName in a few spots, which can differ from classFilename, resulting in invalid imports for a component containing double underscores. I think both these spots should use classFilename instead

openapi-generator/modules/openapi-generator/src/main/resources/python/model_generic.mustache

Line 21 in dc175c5

from {{packageName}}.models.{{model.classVarName}} import {{modelName}}

openapi-generator/modules/openapi-generator/src/main/resources/python/model_generic.mustache

Line 264 in dc175c5

return import_module("{{packageName}}.models.{{model.classVarName}}").{{modelName}}.from_dict(obj)

openapi-generator version

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

Just run python generator with repro spec and look at the Dog__cool import from_dict imports in animal.py
openapi-generator generate -i spec.yaml -g python -o python_client

Repro spec:

openapi: 3.1.0
info:
  title: Animal API
  version: 1.0.0
paths:
  /animals:
    get:
      summary: Get a list of animals
      operationId: getAnimals
      responses:
        '200':
          description: A list of animals
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Animal'
            
components:
  schemas:
    Animal:
      type: object
      discriminator:
        propertyName: type
      required:
        - type
      properties:
        type:
          type: string
          description: The type of the animal
          enum:
            - Cat
            - Dog
        name:
          type: string
          description: The name of the animal
        age:
          type: integer
          description: The age of the animal
          
    Cat:
      type: object
      allOf:
        - $ref: '#/components/schemas/Animal'
        - properties:
            breed:
              type: string
              description: The breed of the cat
            color:
              type: string
              description: The color of the cat
            isIndoor:
              type: boolean
              description: Whether the cat is indoor or outdoor

    Dog__Cool:
      type: object
      allOf:
        - $ref: '#/components/schemas/Animal'
        - properties:
            breed:
              type: string
              description: The breed of the dog
            size:
              type: string
              description: The size of the dog (e.g., small, medium, large)
            isTrained:
              type: boolean
              description: Whether the dog is trained

Related issues/PRs

Suggest a fix

#20273