code: @Override
      protected Content getNavLinkClassUse() {
          Content useLink = getHyperLink(DocPaths.PACKAGE_USE,
                  contents.useLabel, "", "");
          Content li = HtmlTree.LI(useLink);
          return li;
      }
docs: Get "Use" link for this pacakge in the navigation bar.
  
  @return a content tree for the class use link