code: public void addContentsList(Content contentTree, Content contentListTree) {
          Content titleContent = getResource(
                  "doclet.Constants_Summary");
          Content pHeading = HtmlTree.HEADING(HtmlConstants.TITLE_HEADING, true,
                  HtmlStyle.title, titleContent);
          Content div = HtmlTree.DIV(HtmlStyle.header, pHeading);
          Content headingContent = getResource(
                  "doclet.Contents");
          Content heading = HtmlTree.HEADING(HtmlConstants.CONTENT_HEADING, true,
                  headingContent);
          if (configuration.allowTag(HtmlTag.SECTION)) {
              HtmlTree section = HtmlTree.SECTION(heading);
              section.addContent(contentListTree);
              div.addContent(section);
              mainTree.addContent(div);
          } else {
              div.addContent(heading);
              div.addContent(contentListTree);
              contentTree.addContent(div);
          }
      }
docs: {@inheritDoc}