def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'id') and self.id is not None:
            _dict['id'] = self.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'] = self.created
        if hasattr(self, 'updated') and self.updated is not None:
            _dict['updated'] = self.updated
        if hasattr(self, 'url') and self.url is not None:
            _dict['url'] = self.url
        if hasattr(self, 'user_token') and self.user_token is not None:
            _dict['user_token'] = self.user_token
        if hasattr(self, 'results') and self.results is not None:
            _dict['results'] = [x._to_dict() for x in self.results]
        if hasattr(self, 'warnings') and self.warnings is not None:
            _dict['warnings'] = self.warnings
        return _dict
Return a json dictionary representing this model.