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