code: public static HtmlTree MAIN(HtmlStyle styleClass, Content body) {
          HtmlTree htmltree = HtmlTree.MAIN(body);
          if (styleClass != null) {
              htmltree.addStyle(styleClass);
          }
          return htmltree;
      }
docs: Generates a MAIN tag with role attribute, style attribute and some content.
  
  @param styleClass style of the MAIN tag
  @param body content of the MAIN tag
  @return an HtmlTree object for the MAIN tag