[BUG]: `_ClientMixin` is not typed properly

[HenriChabert]

Describe the bug
When using strict typing with Python, and trying to call function find or find_all, I receive the following typing error:

Cannot access attribute "find_all" for class "SubscriptionClient"
 Could not bind method "find_all" because "SubscriptionClient" is not assignable to parameter "self"
   "SubscriptionClient" is incompatible with protocol "_ClientMixin[SubscriptionResponse]"
     "API_RESOURCE" is not defined as a ClassVar in protocol
     "RESPONSE_MODEL" is not defined as a ClassVar in protocol
     "ROOT_NAME" is not defined as a ClassVar in protocolPylance[reportAttributeAccessIssue](https://github.com/microsoft/pyright/blob/main/docs/configuration.md#reportAttributeAccessIssue)

To Reproduce

1. Install lago-python-client
2. Activate strict typing on Python
3. Paste the following code:

from lago_python_client.client import Client as LagoClient

lago_client = LagoClient(
    api_url="https://api.lago.dev",
    api_key="sk_test_1234567890",
)

subscriptions_api = lago_client.subscriptions()
lago_subscriptions = subscriptions_api.find_all()

You should see the following typing error:

Expected behavior
Output type from find_all should not be unknown, and actually be list[SubscriptionResponse]

Screenshots
See above

Support

• OS: macOS Sequoia - Version 15.5
• Browser: Chrome
• Version: lago-python-client == 1.32.0

[HenriChabert]

After investigating the solutions on the codebase, I understand the problem that came up, and that makes things hard to fix. The fact is that ClassVar does not support Generic as parameter, which makes it hard to use in our case.
A proposal would be to still use ClassVar[Type[_PM]] in BaseClient and _ClientMixin and use # type: ignore for this. It seems the variable still works as a ClassVar, and the whole typing work properly. Other changes are just to assign Generic of BaseClient for all clients, for example:

class WalletClient(
    CreateCommandMixin[WalletResponse],
    DestroyCommandMixin[WalletResponse],
    FindAllCommandMixin[WalletResponse],
    FindCommandMixin[WalletResponse],
    UpdateCommandMixin[WalletResponse],
    BaseClient[WalletResponse],
):
    API_RESOURCE: ClassVar[str] = "wallets"
    RESPONSE_MODEL: ClassVar[Type[WalletResponse]] = WalletResponse
    ROOT_NAME: ClassVar[str] = "wallet"

What do you think of that ?