Return a json dictionary representing this model.

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