def get_assessment_taken_notification_session(self, assessment_taken_receiver=None):
raise Unimplemented()<EOL>
Gets the notification session for notifications pertaining to taken assessment changes.

        arg:    assessment_taken_receiver
                (osid.assessment.AssessmentTakenReceiver): the
                assessment taken receiver interface
        return: (osid.assessment.AssessmentTakenNotificationSession) -
                an ``AssessmentTakenNotificationSession``
        raise:  NullArgument - ``assessment_taken_receiver`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented -
                ``supports_assessment_taken_notification()`` is
                ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_assessment_taken_notification()`` is ``true``.*