docs: def _to_dict(self):
          """Return a json dictionary representing this model."""
          _dict = {}
          if hasattr(self, 'name') and self.name is not None:
              _dict['name'] = self.name
          if hasattr(self, 'description') and self.description is not None:
              _dict['description'] = self.description
          if hasattr(self, 'language') and self.language is not None:
              _dict['language'] = self.language
          if hasattr(self, 'metadata') and self.metadata is not None:
              _dict['metadata'] = self.metadata
          if hasattr(self,
                     'learning_opt_out') and self.learning_opt_out is not None:
              _dict['learning_opt_out'] = self.learning_opt_out
          if hasattr(self,
                     'system_settings') and self.system_settings is not None:
              _dict['system_settings'] = self.system_settings._to_dict()
          if hasattr(self, 'workspace_id') and self.workspace_id is not None:
              _dict['workspace_id'] = self.workspace_id
          if hasattr(self, 'status') and self.status is not None:
              _dict['status'] = self.status
          if hasattr(self, 'created') and self.created is not None:
              _dict['created'] = datetime_to_string(self.created)
          if hasattr(self, 'updated') and self.updated is not None:
              _dict['updated'] = datetime_to_string(self.updated)
          if hasattr(self, 'intents') and self.intents is not None:
              _dict['intents'] = [x._to_dict() for x in self.intents]
          if hasattr(self, 'entities') and self.entities is not None:
              _dict['entities'] = [x._to_dict() for x in self.entities]
          if hasattr(self, 'dialog_nodes') and self.dialog_nodes is not None:
              _dict['dialog_nodes'] = [x._to_dict() for x in self.dialog_nodes]
          if hasattr(self,
                     'counterexamples') and self.counterexamples is not None:
              _dict['counterexamples'] = [
                  x._to_dict() for x in self.counterexamples
              ]
          return _dict