code: protected HtmlTree getPackageUseHeader() {
          String packageText = configuration.getText("doclet.Package");
          String name = packageElement.isUnnamed() ? "" : utils.getPackageName(packageElement);
          String title = configuration.getText("doclet.Window_ClassUse_Header", packageText, name);
          HtmlTree bodyTree = getBody(true, getWindowTitle(title));
          HtmlTree htmlTree = (configuration.allowTag(HtmlTag.HEADER))
                  ? HtmlTree.HEADER()
                  : bodyTree;
          addTop(htmlTree);
          addNavLinks(true, htmlTree);
          if (configuration.allowTag(HtmlTag.HEADER)) {
              bodyTree.addContent(htmlTree);
          }
          ContentBuilder headContent = new ContentBuilder();
          headContent.addContent(contents.getContent("doclet.ClassUse_Title", packageText));
          headContent.addContent(new HtmlTree(HtmlTag.BR));
          headContent.addContent(name);
          Content heading = HtmlTree.HEADING(HtmlConstants.TITLE_HEADING, true,
                  HtmlStyle.title, headContent);
          Content div = HtmlTree.DIV(HtmlStyle.header, heading);
          if (configuration.allowTag(HtmlTag.MAIN)) {
              mainTree.addContent(div);
          } else {
              bodyTree.addContent(div);
          }
          return bodyTree;
      }
docs: Get the header for the package use listing.
  
  @return a content tree representing the package use header