docs: def _get_order_by(self, request):
          """ Return an SA order_by """
          attr = request.params.get('sort', request.params.get('order_by'))
          if attr is None or not hasattr(self.mapped_class, attr):
              return None
          if request.params.get('dir', '').upper() == 'DESC':
              return desc(getattr(self.mapped_class, attr))
          else:
              return asc(getattr(self.mapped_class, attr))