Not imported : from lantz.ui.qtwidgets import start_test_app

Hello,
I may have found information to update in :
http://lantz.readthedocs.io/en/latest/tutorial/building.html#beautiful-testing
The code from lantz.ui.qtwidgets import start_test_app is not working. Qtwigets can't be imported
I have found in the source the working code from lantz.ui.app import start_test_app
Is this the new class to use to auto-build GUI ? Documentation is to update?
By the way , Lantz is great!
Goodbye