Embed app into PYQT5 GUI with HWND (window handle)

Question

How can i embed an app window into a pyqt5 GUI using its windows handle? I have gotten to the point where i can get the handle of the window, but trying to embed it causes the script to crash with no error code before the GUI window is created

_driver = webdriver.Firefox()
my_dict = _driver.capabilities
PID = my_dict['moz:processID']
hwnd = win32gui.FindWindow('notepad', None)

(hwnd is the handle). Here is the code I use to embed the app, it stops working at the line

window = QWindow.fromWinId(hwnd)


class Browser(QWindow):
    def __init__(self):
        print("making app")
        window = QWindow.fromWinId(hwnd)
        widget = QtWidgets.createWindowContainer(window)
        widget.setParent(self)
        layout = QVBoxLayout(self)
        layout.addWidget(widget)
        self.setLayout(layout)
        self.setFixedSize(1000, 1000)

Here is how I call the app:

if __name__ == "__main__":
    main = Browser()
    app = QApplication(sys.argv)
    _window = QWindow()
    _window.show()
    sys.exit(app.exec_())