如何在PyQt5中制作嵌套的StackedLayouts？

from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QHBoxLayout, QStackedLayout, QPushButton

app = QApplication([])
window = QWidget()
layout = QVBoxLayout()
window.setLayout(layout)

# 子窗口1
sub_window1 = QWidget()
sub_layout1 = QHBoxLayout()
sub_button1 = QPushButton("Sub Window 1")
sub_layout1.addWidget(sub_button1)
sub_window1.setLayout(sub_layout1)

# 子窗口2
sub_window2 = QWidget()
sub_layout2 = QHBoxLayout()
sub_button2 = QPushButton("Sub Window 2")
sub_layout2.addWidget(sub_button2)
sub_window2.setLayout(sub_layout2)

stacked_layout = QStackedLayout()
stacked_layout.addWidget(sub_window1)
stacked_layout.addWidget(sub_window2)

button1 = QPushButton("Show Sub Window 1")
button2 = QPushButton("Show Sub Window 2")

def show_sub_window1():
    stacked_layout.setCurrentWidget(sub_window1)

def show_sub_window2():
    stacked_layout.setCurrentWidget(sub_window2)

button1.clicked.connect(show_sub_window1)
button2.clicked.connect(show_sub_window2)

layout.addWidget(button1)
layout.addWidget(button2)
layout.addLayout(stacked_layout)

window.show()
app.exec_()