[Question][Python-fastapi] Implementing a singleton pattern for BaseApi subclasses to prevent initialization

Description

With the current structure, every time an endpoint is called, a new instance of the BaseApi subclass is initialized. How can I implement a singleton to prevent this?

openapi-generator version

v7.0.1 and snapshot version.

OpenAPI declaration file content or url

Here is an example of the OpenAPI declaration file content:

https://gist.github.com/reyescabello/6cd965708fd0b03e8eadb9f3c0c0a899

Generation Details

Generated with jar:

java -jar openapi-generator-cli.jar generate -i openapi.yml -g python-fastapi -o openapi_server

Steps to reproduce

Generated files:

product_api.py

async def find_product_by_id(
    id: str = Path(None, description="ID of product to return", max_length=20),
) -> Product:
    """The user must have any permission in the application."""
    return BaseProductApi.subclasses[0]().find_product_by_id(id)

product_api_base.py

class BaseProductApi:
    subclasses: ClassVar[Tuple] = ()

    def __init_subclass__(cls, **kwargs):
        print(super().__init_subclass__(**kwargs))
        BaseProductApi.subclasses = BaseProductApi.subclasses + (cls,)

The BaseProductApi subclass that I have created. The singleton is not working:

class SubclassProductApi(BaseProductApi):
    __metaclass__ = Singleton

Start by reviewing the generated product_api.py and product_api_base.py examples, then run the reported Java generation command with the linked OpenAPI declaration. Check how BaseProductApi.subclasses is populated and how the endpoint instantiates its implementation. Done would require a clearly specified generator-supported approach that prevents repeated initialization without breaking generated server behavior.