Typing bug in FeatureManager.is_enabled overloads: single argument call not supported by type hints

FeatureManager.is_enabled のオーバーロード宣言を見つけ、この issue にある実行時シグネチャおよび単一引数の例と比較します。不足している1引数の型付けバリアントを追加し、静的解析が呼び出しを受け入れて bool を推論することを確認します。

• Package Version: 2.1.0
• Operating System: Ubuntu
• Python Version: 3.12

Describe the bug
The FeatureManager.is_enabled method has incorrect type hints in the published SDK.

The implementation accepts a single argument:

await feature_manager.is_enabled("my-flag")

This works at runtime because the method signature is:

async def is_enabled(self, feature_flag_id: str, *args, **kwargs) -> bool

However, the declared overloads do not include a signature that accepts only one argument. The only available overload is:

@overload
async def is_enabled(self, feature_flag_id: str, user_id: str, **kwargs) -> bool:
    ...

Type checkers such as Mypy report this usage as invalid and treat the return type as Any.

Expected Behavior
The type hints should describe all valid usages. Since the runtime implementation allows calling the method with only feature_flag_id, the overloads should include a matching variant.

Proposed Fix
Add a second overload:

@overload
async def is_enabled(self, feature_flag_id: str) -> bool:
    ...

This aligns the type hints with the implementation and returns the correct bool type to static analysis tools.