'Ensure that field question_id XOR field question_id_2 is not null'

@api.constrains('question_id', 'question_id_2')
def _check_question_not_empty(self):

    if (not (bool(self.question_id) != bool(self.question_id_2))):
        raise ValidationError('A    label    must    be    attached    to    one    and    only    one    question')
