code: public void addRespondToURL(String label, String url) {
  
      RespondToURL respondToURL = new RespondToURL();
      respondToURL.label = label;
      respondToURL.url = url;
  
      respondToURLs.add(respondToURL);
  
    }
docs: Add a response URL to the probe.
  
  @param label the string label for the respondTo address
  @param url the actual URL string