def get_assessment_offered_notification_session(self, assessment_offered_receiver=None, proxy=None):
if proxy is None:<EOL><INDENT>raise NullArgument()<EOL><DEDENT>raise Unimplemented()<EOL>
Gets the notification session for notifications pertaining to offered assessment changes.

        arg:    assessment_offered_receiver
                (osid.assessment.AssessmentOfferedReceiver): the
                assessment offered receiver interface
        arg:    proxy (osid.proxy.Proxy): a proxy
        return: (osid.assessment.AssessmentOfferedNotificationSession) -
                an ``AssessmentOfferedNotificationSession``
        raise:  NullArgument - ``assessment_offered_receiver`` or
                ``proxy`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented -
                ``supports_assessment_offered_notification()`` is
                ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_assessment_offered_notification()`` is ``true``.*