[BUG] [Python] Problems with nested `allOf` -> `anyOf` types

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• 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?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Generated Python code seemingly fails to properly deserialize allOf with nested anyOf objects.
Given following input:

from openapi_client.models.availability_with_shipping_time import AvailabilityWithShippingTime
DATA = {'availability': {'type': 'Stock', 'shipping_time_in_days': None}}
AvailabilityWithShippingTime.from_dict(DATA)

openapi-generator version

openapi-generator-cli 7.18.0

OpenAPI declaration file content or url

openapi: 3.1.0
info:
  contact:
    email: info@example.org
  title: API
  version: 1.0.0
paths:
  /availability:
    get:
      operationId: getAvailability
      responses:
        '200':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/AvailabilityWithShippingTime'
          description: Example
components:
  schemas:
    Availability:
      oneOf:
        - type: object
          description: There is sufficient stock for the required quantity.
          required:
            - type
          properties:
            type:
              type: string
              enum:
                - Stock
        - type: object
          description: |-
            There is not sufficient stock, but enough stock with on order quantities
            by the given lead time in days.
          required:
            - days
            - type
          properties:
            days:
              type: integer
              format: int64
              description: |-
                There is not sufficient stock, but enough stock with on order quantities
                by the given lead time in days.
              minimum: 0
            type:
              type: string
              enum:
                - OnOrder
        - type: object
          description: |-
            There is not sufficient stock, but enough stock with on order quantities
            without a given date or lead time
          required:
            - type
          properties:
            type:
              type: string
              enum:
                - OnOrderWithUnknownLeadTime
        - type: object
          description: |-
            There is not sufficient stock, even with on order quantities, but there is a given
            factory lead time by which the required quantity can be obtained.
          required:
            - days
            - type
          properties:
            days:
              type: integer
              format: int64
              description: |-
                There is not sufficient stock, even with on order quantities, but there is a given
                factory lead time by which the required quantity can be obtained.
              minimum: 0
            type:
              type: string
              enum:
                - LeadTimeDays
      description: |-
        Availability of a solution or purchase option, indicating if it is in stock
        or the method and number of days until the required quantity is obtained.
    AvailabilityWithShippingTime:
      allOf:
        - $ref: '#/components/schemas/Availability'
        - type: object
          properties:
            shipping_time_in_days:
              type:
                - integer
                - 'null'
              format: int64
              minimum: 0

Generation Details

openapi-generator-cli generate -i allof-anyof-bundle.yaml -g python -o outputdir

Steps to reproduce

1. Get the yaml openapi bundle from this issue report
2. Generate python code using openapi-generator-cli generate -i allof-anyof-bundle.yaml -g python -o outputdir
3. Place the example python code given in description in the outputdir
4. Run the python code and see conclude that it fails to deserialize the AvailabilityWithShippingTime object properly...

Related issues/PRs

There are many similar issues given, though they are not related to Python or do not have proper reproduction steps...

Start by running the reported generation command with allof-anyof-bundle.yaml, then inspect the generated AvailabilityWithShippingTime and Availability model deserialization around from_dict. Use the supplied DATA example to reproduce the failure. Done means the nested allOf/anyOf data deserializes into the expected Python object without losing the shipping_time_in_days value.