def get_agency_notification_session(self, agency_receiver=None):
raise Unimplemented()<EOL>
Gets the notification session for notifications pertaining to agency service changes.

        arg:    agency_receiver (osid.authentication.AgencyReceiver):
                the agency receiver
        return: (osid.authentication.AgencyNotificationSession) - an
                ``AgencyNotificationSession``
        raise:  NullArgument - ``agency_receiver`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_agency_notification()`` is
                ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_agency_notification()`` is ``true``.*