docs: def _to_dict(self):
          """Return a json dictionary representing this model."""
          _dict = {}
          if hasattr(self, 'classifier_id') and self.classifier_id is not None:
              _dict['classifier_id'] = self.classifier_id
          if hasattr(self, 'name') and self.name is not None:
              _dict['name'] = self.name
          if hasattr(self, 'owner') and self.owner is not None:
              _dict['owner'] = self.owner
          if hasattr(self, 'status') and self.status is not None:
              _dict['status'] = self.status
          if hasattr(self,
                     'core_ml_enabled') and self.core_ml_enabled is not None:
              _dict['core_ml_enabled'] = self.core_ml_enabled
          if hasattr(self, 'explanation') and self.explanation is not None:
              _dict['explanation'] = self.explanation
          if hasattr(self, 'created') and self.created is not None:
              _dict['created'] = datetime_to_string(self.created)
          if hasattr(self, 'classes') and self.classes is not None:
              _dict['classes'] = [x._to_dict() for x in self.classes]
          if hasattr(self, 'retrained') and self.retrained is not None:
              _dict['retrained'] = datetime_to_string(self.retrained)
          if hasattr(self, 'updated') and self.updated is not None:
              _dict['updated'] = datetime_to_string(self.updated)
          return _dict