pyside QGraphicsItemGroup.childItems() changes after a return

The result returned by method childItems()on an instance QGraphicsItemGroup differs before and after a simple return of the instance in PySide.

Attached file demos the problem.

Before the return, it prints a non-empty list for childItems().
After the return, it prints an empty list.

The attached demo is a reduction but I think the problem exists in my larger app.

I haven't found a workaround yet but adding the graphic items to the scene first might help?

Could it be a garbage collection problem of an instance that is only on the stack?