docs: def _endpoint(self, endpoint, action, *url_args):
          """Return the URL for the action.
  
          :param str endpoint: The controller
          :param str action: The action provided by the controller
          :param url_args: Additional endpoints(for endpoints that take part of
                           the url as option)
          :return: Full URL for the requested action
          """
          args = (self.api_base, endpoint, action)
          if action == '':
              args = (self.api_base, endpoint)
          api_url = "/".join(args)
          if url_args:
              if len(url_args) == 1:
                  api_url += "/" + url_args[0]
              else:
                  api_url += "/".join(url_args)
          return api_url