Add and implement new IncompleteCredentialError in bfxapi.client.

bfxapi/websocket/_client/bfx_websocket_client.py

@@ -36,13 +36,12 @@ from .bfx_websocket_bucket import BfxWebSocketBucket
 from .bfx_websocket_inputs import BfxWebSocketInputs
 
 if TYPE_CHECKING:
+    from bfxapi.client import _Credentials
+
     from asyncio import Task
 
     _T = TypeVar("_T", bound=Callable[..., None])
 
-    _Credentials = TypedDict("_Credentials", \
-        { "api_key": str, "api_secret": str, "filters": Optional[List[str]] })
-
     _Reconnection = TypedDict("_Reconnection",
         { "attempts": int, "reason": str, "timestamp": datetime })