code: public OrderColumn<ElementCollection<T>> getOrCreateOrderColumn()
     {
        Node node = childNode.getOrCreate("order-column");
        OrderColumn<ElementCollection<T>> orderColumn = new OrderColumnImpl<ElementCollection<T>>(this, "order-column", childNode, node);
        return orderColumn;
     }
docs: If not already created, a new <code>order-column</code> element with the given value will be created.
  Otherwise, the existing <code>order-column</code> element will be returned.
  @return  a new or existing instance of <code>OrderColumn<ElementCollection<T>></code>