@abc.abstractmethod<EOL><INDENT>def get_commitment_notification_session(self, commitment_receiver):<DEDENT>
return<EOL>
Gets the notification session for notifications pertaining to commitment changes.

        :param commitment_receiver: the commitment receiver
        :type commitment_receiver: ``osid.calendaring.CommitmentReceiver``
        :return: a ``CommitmentNotificationSession``
        :rtype: ``osid.calendaring.CommitmentNotificationSession``
        :raise: ``NullArgument`` -- ``commitment_receiver`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_commitment_notification()`` is ``false``

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