def _on_join_complete(self, generation, member_id, protocol,
                          member_assignment_bytes):
        """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.
        """
        pass
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.
        
kafka/coordinator/base.py