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

        :param vaultreceiver: the vault receiver
        :type vaultreceiver: ``osid.authorization.VaultReceiver``
        :return: a ``VaultNotificationSession``
        :rtype: ``osid.authorization.VaultNotificationSession``
        :raise: ``NullArgument`` -- ``vault_receiver`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_vault_notification() is false``

        *compliance: optional -- This method must be implemented if
        ``supports_vault_notification()`` is true.*