Stop managing a group

def remove_multizone(self, group_uuid):
        """ Stop managing a group """
        group_uuid = str(group_uuid)
        group = self._groups.pop(group_uuid, None)
        # Inform all group members that they are no longer members
        if group is not None:
            group['listener']._mz.reset_members()  # noqa: E501 pylint: disable=protected-access
        for member in self._casts.values():
            member['groups'].discard(group_uuid)