Type error for multiple inheritance using typing.Generic

from PySide6.QtWidgets import QApplication, QMainWindow, QLabel
from typing import Generic, TypeVar

ItemType = TypeVar("ItemType")


class MainWindow(QMainWindow, Generic[ItemType]):
    def __init__(self):
        QMainWindow.__init__(self, parent=None)
        self.resize(400, 300)
        self.lbl = QLabel(self)
        self.lbl.setText("XXX")


app = QApplication([])
window = MainWindow()
window.show()
app.exec()

Traceback (most recent call last):
  File "/home/mark/git/napari/foo.py", line 16, in <module>
    window = MainWindow()
  File "/home/mark/git/napari/foo.py", line 9, in __init__
    QMainWindow.__init__(self, parent=None)
TypeError: object.__init__() takes exactly one argument (the instance to initialize)