code: protected URL extractURL(Object url)
      throws IOException {
      if (!(url instanceof String)) {
        return null;
      }
      return (null == url || "".equals(url)) ? null : new URL( (String) url);
    }
docs: Extracts a URL from a result that consists of a URL only.
  For JSON, that result is simply a String.
  @param url
  @return the URL