Defining a user property with a python list as the type doesn't work with QDataWidgetMapper. 

it doesn't even call the setter method.

it works with PyQt5 and after some searching i found that it works with PySide2 if the Property is defined with "QVariantList" instead but that's not pythonic.

More strangely; it will work if i change the model data method to return a tuple instead of a list !!!

I've attached a file to reproduce the issue.