Hi Cheng, I had expected that flatten_data would "do the right thing" but as you demonstrate it seems that the manipulator doesn't flatten it correctly either.
The CheckboxField expects booleans to be "on" for True and "" for False so i guess this is what the manipulator should flatten to, rather than 1 or 0 - but there may be string attached here - I don't know. I suggest you file a bug report. Goodnight. Kieran
