Writing docstring for custom PySide6 class

Question

I am subclassing PySide6.QtCore.QObject and writing class docstring. However, __doc__ is returning None instead of my docstring.

>>> from PySide6.QtCore import QObject
>>> class MyObj(QObject):
...     """My docstring."""
>>> MyObj.__doc__ is None
True

Is this a bug, or do I need to use some other way to document my class? I am currently using PySide6==6.3.0.