如何在已有的qtabwidget中添加子标签？

from PyQt5.QtWidgets import QApplication, QMainWindow, QTabWidget, QWidget, QVBoxLayout, QLabel

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

        self.setWindowTitle("QTabWidget Example")
        self.setGeometry(100, 100, 400, 300)

        tab_widget = QTabWidget(self)
        self.setCentralWidget(tab_widget)

        # 创建第一个子标签
        tab1 = QWidget()
        layout1 = QVBoxLayout(tab1)
        label1 = QLabel("This is Tab 1")
        layout1.addWidget(label1)
        tab_widget.addTab(tab1, "Tab 1")

        # 创建第二个子标签
        tab2 = QWidget()
        layout2 = QVBoxLayout(tab2)
        label2 = QLabel("This is Tab 2")
        layout2.addWidget(label2)
        tab_widget.addTab(tab2, "Tab 2")

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