How to use the psiturk.models.Participant.beginhit.desc function in PsiTurk

def unreject_assignment(self, assignment_id, all_studies=False):
        ''' Unreject assignment '''
        response = self.amt_services.unreject_assignment(assignment_id)
        result = {}
        if not response.success:
            raise response.exception
        else:
            message='unrejected {}'.format(assignment_id)
            try:
                participant = Participant.query\
                    .filter(Participant.assignmentid == assignment_id)\
                    .order_by(Participant.beginhit.desc()).first()
                participant.status = CREDITED
                db_session.add(participant)
                db_session.commit()
            except:
                message = '{} but failed to update local db'.format(
                    message)
        return message