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

        arg:    vaultreceiver (osid.authorization.VaultReceiver): the
                vault receiver
        return: (osid.authorization.VaultNotificationSession) - a
                ``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.*