code: def _add_nonce(self, response):
          
          nonce = response.headers.getRawHeaders(
              REPLAY_NONCE_HEADER, [None])[0]
          with LOG_JWS_ADD_NONCE(raw_nonce=nonce) as action:
              if nonce is None:
                  raise errors.MissingNonce(response)
              else:
                  try:
                      decoded_nonce = Header._fields['nonce'].decode(
                          nonce.decode('ascii')
                      )
                      action.add_success_fields(nonce=decoded_nonce)
                  except DeserializationError as error:
                      raise errors.BadNonce(nonce, error)
                  self._nonces.add(decoded_nonce)
                  return response
docs: Store a nonce from a response we received.
  
          :param twisted.web.iweb.IResponse response: The HTTP response.
  
          :return: The response, unmodified.