code: public void setIndex(int index) {
          ElementBase parent = getParent();
          
          if (parent == null) {
              CWFException.raise("Element has no parent.");
          }
          
          int currentIndex = parent.children.indexOf(this);
          
          if (currentIndex < 0 || currentIndex == index) {
              return;
          }
          
          parent.moveChild(currentIndex, index);
      }
docs: Sets this element's index to the specified value. This effectively changes the position of
  the element relative to its siblings.
  
  @param index The index.