When setting a widget's parent to None, PyCharm's type checker complains that the type is invalid. This is however valid code but the stub files distributed with PySide6 are incorrect.

tab_widget.setParent(None)

The stubs do not allow the parent to be None.

@overload
def setParent(self, parent: PySide6.QtWidgets.QWidget) -> None: ...
@overload
def setParent(self, parent: PySide6.QtWidgets.QWidget, f: PySide6.QtCore.Qt.WindowType) -> None: ...

 The solution is to either make the type optional or add another overload.

I believe these stubs are generated somehow so I don't know how you would handle this.

PYSIDE-1675 is the ticket tracking issues like this I believe.