Return a json dictionary representing this model.

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