@abc.abstractmethod<EOL><INDENT>def get_time_period_notification_session(self, time_period_receiver):<DEDENT>
return<EOL>
Gets the notification session for notifications pertaining to time period changes.

        :param time_period_receiver: the time period receiver
        :type time_period_receiver: ``osid.calendaring.TimePeriodReceiver``
        :return: a ``TimePeriodNotificationSession``
        :rtype: ``osid.calendaring.TimePeriodNotificationSession``
        :raise: ``NullArgument`` -- ``time_period_receiver`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_time_period_notification()`` is ``false``

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