Jquery sortable serialize gives array of empty objects

Jquery sortable serialize gives array of empty objects

I'm using http://johnny.github.io/jquery-sortable/ not Jquery UI sortable.
My full code is here: http://jsfiddle.net/shankardevy/XwkxH/2/
jQuery('.draggable').sortable({
onDrop: function (item, container, _super) {
console.log($('.draggable').sortable("serialize").get());
_super(item, container)
}
})
My problem is that in the above code, sortable('serialize') as documented
in http://johnny.github.io/jquery-sortable/ is not working for me. It
gives me an array of empty objects while I expect the array to contain the
<li> objects in the order sorted.