code: public HtmlTree getStyleSheetProperties() {
          String stylesheetfile = configuration.stylesheetfile;
          DocPath stylesheet;
          if (stylesheetfile.isEmpty()) {
              stylesheet = DocPaths.STYLESHEET;
          } else {
              DocFile file = DocFile.createFileForInput(configuration, stylesheetfile);
              stylesheet = DocPath.create(file.getName());
          }
          HtmlTree link = HtmlTree.LINK("stylesheet", "text/css",
                  pathToRoot.resolve(stylesheet).getPath(),
                  "Style");
          return link;
      }
docs: Returns a link to the stylesheet file.
  
  @return an HtmlTree for the lINK tag which provides the stylesheet location