def get_grade_entry_notification_session(self, receiver=None):
raise Unimplemented()<EOL>
Gets the notification session for notifications pertaining to grade entry changes.

        arg:    receiver (osid.grading.GradeEntryReceiver): the grade
                entry receiver
        return: (osid.grading.GradeEntryNotificationSession) - a
                ``GradeEntryNotificationSession``
        raise:  NullArgument - ``receiver`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_grade_entry_notification()``
                is ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_grade_entry_notification()`` is ``true``.*