code: public boolean insertBeforeId(String id, String insString)
              throws TagTypeUnmatchException {
          return InsertByIdUtil.insertBeforeId(id, insString, this);
      }
docs: <p>insert string before the element having specified id attribute.</p>
  
  @param id
  @param insString
  @return true if success to insert. if no hit, return false.
  @throws TagTypeUnmatchException