code: public static void generate(ConfigurationImpl configuration,
              PackageDoc packageDoc) {
          PackageFrameWriter packgen;
          try {
              packgen = new PackageFrameWriter(configuration, packageDoc);
              String pkgName = Util.getPackageName(packageDoc);
              Content body = packgen.getBody(false, packgen.getWindowTitle(pkgName));
              Content pkgNameContent = new StringContent(pkgName);
              Content heading = HtmlTree.HEADING(HtmlConstants.TITLE_HEADING, HtmlStyle.bar,
                      packgen.getTargetPackageLink(packageDoc, "classFrame", pkgNameContent));
              body.addContent(heading);
              HtmlTree div = new HtmlTree(HtmlTag.DIV);
              div.addStyle(HtmlStyle.indexContainer);
              packgen.addClassListing(div);
              body.addContent(div);
              packgen.printHtmlDocument(
                      configuration.metakeywords.getMetaKeywords(packageDoc), false, body);
              packgen.close();
          } catch (IOException exc) {
              configuration.standardmessage.error(
                      "doclet.exception_encountered",
                      exc.toString(), DocPaths.PACKAGE_FRAME.getPath());
              throw new DocletAbortException(exc);
          }
      }
docs: Generate a package summary page for the left-hand bottom frame. Construct
  the PackageFrameWriter object and then uses it generate the file.
  
  @param configuration the current configuration of the doclet.
  @param packageDoc The package for which "pacakge-frame.html" is to be generated.