code: public static MarkedElement markup(IRenderingElement elem, String... classes) {
          assert elem != null;
          MarkedElement tagElem = new MarkedElement(elem);
          for (String cls : classes)
              tagElem.aggClass(cls);
          return tagElem;
      }
docs: Markup a rendering element with the specified classes.
  
  @param elem rendering element
  @param classes classes
  @return the marked element