code: def href_for(self, operation, qs=None, **kwargs):
          
          url = urljoin(request.url_root, self.url_for(operation, **kwargs))
          qs_character = "?" if url.find("?") == -1 else "&"
  
          return "{}{}".format(
              url,
              "{}{}".format(qs_character, urlencode(qs)) if qs else "",
          )
docs: Construct an full href for an operation against a resource.
  
          :parm qs: the query string dictionary, if any
          :param kwargs: additional arguments for path expansion