def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'score') and self.score is not None:
            _dict['score'] = self.score
        if hasattr(self, 'confidence') and self.confidence is not None:
            _dict['confidence'] = self.confidence
        return _dict
Return a json dictionary representing this model.