code: def before_request(self, request, method, url, headers):
          
          # pylint: disable=unused-argument
          # (pylint doesn't correctly recognize overridden methods.)
          parts = urllib.parse.urlsplit(url)
          # Strip query string and fragment
          audience = urllib.parse.urlunsplit(
              (parts.scheme, parts.netloc, parts.path, "", ""))
          token = self._get_jwt_for_audience(audience)
          self.apply(headers, token=token)
docs: Performs credential-specific before request logic.
  
          Args:
              request (Any): Unused. JWT credentials do not need to make an
                  HTTP request to refresh.
              method (str): The request's HTTP method.
              url (str): The request's URI. This is used as the audience claim
                  when generating the JWT.
              headers (Mapping): The request's headers.