@abc.abstractmethod<EOL><INDENT>def get_agency_notification_session(self, agency_receiver):<DEDENT>
return<EOL>
Gets the notification session for notifications pertaining to agency service changes.

        :param agency_receiver: the agency receiver
        :type agency_receiver: ``osid.authentication.AgencyReceiver``
        :return: an ``AgencyNotificationSession``
        :rtype: ``osid.authentication.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``.*