code: protected Content getPackageTreeHeader() {
          String title = packagedoc.name() + " " +
                  configuration.getText("doclet.Window_Class_Hierarchy");
          Content bodyTree = getBody(true, getWindowTitle(title));
          addTop(bodyTree);
          addNavLinks(true, bodyTree);
          return bodyTree;
      }
docs: Get the package tree header.
  
  @return a content tree for the header