三级深度Jquery sortbable问题

Question

 I have three levels of jQuery sortable divs,
 all having draggable, droppable and sortable features.

 The moment I put the the third sortable div inside the second div,
 and drag them  around, i get this error : 

>HierarchyRequestError: Failed to execute 'appendChild' on 'Node': 
The new child element contains the parent./jquery.js            

我知道这是因为孩子正在试图控制自己。  但是，有没有人有任何其他技巧，他们可以帮助我， 这样可以巧妙地克服jQuery sortable的这种限制吗？

 I want to extend this http://jsfiddle.net/ExLqv/12
 with three levels of nesting.