'Invoked when a group member has successfully joined a group.
Arguments:
generation (int): the generation that was joined
member_id (str): the identifier for the local member in the group
protocol (str): the protocol selected by the coordinator
member_assignment_bytes (bytes): the protocol-encoded assignment
propagated from the group leader. The Coordinator instance is
responsible for decoding based on the chosen protocol.'

@abc.abstractmethod
def _on_join_complete(self, generation, member_id, protocol, member_assignment_bytes):

    pass
