code: def _url_format(self, service):
          
          base_service_url = '{base}{service}'.format(
              base=self.urlbase,
              service=service
          )
          return base_service_url
docs: Generate URL from urlbase and service.
  
          Args:
              service (str): The endpoint service to use, i.e. gradebook
          Returns:
              str: URL to where the request should be made