docs: String getHiddenInputHtmlForRequestParameters() {
          StringBuilder html = new StringBuilder();
          if (parameterMap != null) {
              Set<Entry<String, String[]>> entries = parameterMap.entrySet();
              for (Entry<String, String[]> entry : entries) {
                  html.append(getHiddenInputForRequestParam(entry));
              }
          }
          return html.toString();
      }