code: def to_dict(self):
          
          return {
              'model_type': 'discretechoice',
              'model_expression': self.model_expression,
              'sample_size': self.sample_size,
              'name': self.name,
              'probability_mode': self.probability_mode,
              'choice_mode': self.choice_mode,
              'choosers_fit_filters': self.choosers_fit_filters,
              'choosers_predict_filters': self.choosers_predict_filters,
              'alts_fit_filters': self.alts_fit_filters,
              'alts_predict_filters': self.alts_predict_filters,
              'interaction_predict_filters': self.interaction_predict_filters,
              'estimation_sample_size': self.estimation_sample_size,
              'prediction_sample_size': self.prediction_sample_size,
              'choice_column': self.choice_column,
              'fitted': self.fitted,
              'log_likelihoods': self.log_likelihoods,
              'fit_parameters': (yamlio.frame_to_yaml_safe(self.fit_parameters)
                                 if self.fitted else None)
          }
docs: Return a dict respresentation of an MNLDiscreteChoiceModel
          instance.