PySide6 does not support QQuickAttachedPropertyPropagator

PySide6 seems to not support QQuickAttachedPropertyPropagator because using the following code results in an error:

@QmlNamedElement("FluentUI") 
@QmlAttached(FluentUI)
class FluentUI(QQuickAttachedPropertyPropagator):

However, if I write it in a split manner like this:

@QmlAnonymous
class FluentStyleAttached(QQuickAttachedPropertyPropagator):
@QmlNamedElement("FluentUI")
@QmlAttached(FluentStyleAttached) 

The attachedParentChange method does not get triggered.

How can I resolve this issue?