docs: def _to_dict(self):
          """Return a json dictionary representing this model."""
          _dict = {}
          if hasattr(self, 'total_examples') and self.total_examples is not None:
              _dict['total_examples'] = self.total_examples
          if hasattr(self, 'available') and self.available is not None:
              _dict['available'] = self.available
          if hasattr(self, 'processing') and self.processing is not None:
              _dict['processing'] = self.processing
          if hasattr(self, 'minimum_queries_added'
                    ) and self.minimum_queries_added is not None:
              _dict['minimum_queries_added'] = self.minimum_queries_added
          if hasattr(self, 'minimum_examples_added'
                    ) and self.minimum_examples_added is not None:
              _dict['minimum_examples_added'] = self.minimum_examples_added
          if hasattr(self, 'sufficient_label_diversity'
                    ) and self.sufficient_label_diversity is not None:
              _dict[
                  'sufficient_label_diversity'] = self.sufficient_label_diversity
          if hasattr(self, 'notices') and self.notices is not None:
              _dict['notices'] = self.notices
          if hasattr(self, 'successfully_trained'
                    ) and self.successfully_trained is not None:
              _dict['successfully_trained'] = datetime_to_string(
                  self.successfully_trained)
          if hasattr(self, 'data_updated') and self.data_updated is not None:
              _dict['data_updated'] = datetime_to_string(self.data_updated)
          return _dict