Hi, I'm trying to fix the error with `handle` widget. The problem occurs upon swapping out task rank, it gives me an `assertion error` since I'm using different property instead of `sequence`.

Here's the screenshot upon re-arranging the tasks:

http://prntscr.com/au0f42

See my code snippet:

https://gist.github.com/renesansz/0a07f6bd64ef25fd300b87001de74c05

Any help will be appreciated.

Thanks