如何连接两个QComboBox，使第二个只显示某些项目？

from PyQt5.QtWidgets import QApplication, QMainWindow, QComboBox

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        self.combo1 = QComboBox(self)
        self.combo1.addItem("Option 1")
        self.combo1.addItem("Option 2")
        self.combo1.addItem("Option 3")
        self.combo1.currentIndexChanged.connect(self.updateCombo2)

        self.combo2 = QComboBox(self)

        self.setCentralWidget(self.combo1)

    def updateCombo2(self, index):
        self.combo2.clear()
        if index == 0:
            self.combo2.addItem("Option A")
            self.combo2.addItem("Option B")
        elif index == 1:
            self.combo2.addItem("Option C")
            self.combo2.addItem("Option D")
        elif index == 2:
            self.combo2.addItem("Option E")
            self.combo2.addItem("Option F")

if __name__ == "__main__":
    app = QApplication([])
    window = MainWindow()
    window.show()
    app.exec_()