def get_relationship_notification_session(self, relationship_receiver=None, proxy=None):
if proxy is None:<EOL><INDENT>raise NullArgument()<EOL><DEDENT>raise Unimplemented()<EOL>
Gets the ``OsidSession`` associated with the relationship notification service.

        arg:    relationship_receiver
                (osid.relationship.RelationshipReceiver): the receiver
        arg:    proxy (osid.proxy.Proxy): a proxy
        return: (osid.relationship.RelationshipNotificationSession) - a
                ``RelationshipNotificationSession``
        raise:  NullArgument - ``relationship_receiver`` or ``proxy`` is
                ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_relationship_notification()``
                is ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_relationship_notification()`` is ``true``.*