def get_group_assignment_session(self):
raise Unimplemented()<EOL>
Gets the session for assigning resources to groups.

        return: (osid.resource.GroupAssignmentSession) - a
                ``GroupAssignmentSession``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_group_assignment()`` is
                ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_group_assignment()`` is ``true``.*