Token should be able to be None in FFS method `_get_meta_data`.

[ribeirojose]

As the token can be set in the instance, one should be able to call this method with no args (its logic already assumes that).

pygate-gRPC/pygate_grpc/ffs.py

Line 215 in c98019f

def _get_meta_data(self, token: str) -> Tuple[Tuple[str, str]]: