It's not clear from documentation and example if it's possible to create a custom widget in addpagemethod

Reading the documentation at Creating Custom Widgets for Qt Designer page and trying to play with the `containerextension` example is not clear if it's possible to create a container that have custom widgets as children, but only QWidgets, so no custom properties.

So I wonder if this is possible and how to achieve it, and possibly to document or modify the containerextension example to reflect this feature.