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