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