def order_by(self, *order_by):
    order_by = _process_order_by(self._model_class, order_by)
    _order_by = (self._order_by + list(order_by))
    return self._update(_order_by=_order_by)
def order_by(self, *order_by):
    order_by = _process_order_by(self._model_class, order_by)
    _order_by = (self._order_by + list(order_by))
    return self._update(_order_by=_order_by)