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