Python qt designer中只显示一个菜单

我正在使用qt设计器设计GUI。我正在将UI转换为代码并在pycharm中运行它。当我在qt designer中创建带有2个菜单的主窗口时： Flie->[导入，退出] 文件是主菜单，导入和退出是子菜单。仅显示第一个子菜单。当我在qt设计器中设计时，它会显示出来，但当我在qt设计器中运行它时，只会显示第一个。生成的代码如下所示：

# -*- coding: utf-8 -*-

# Form implementation generated from reading ui file 'test.ui'
#
# Created by: PyQt5 UI code generator 5.12.1
#
# WARNING! All changes made in this file will be lost!

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(800, 600)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 22))
        self.menubar.setObjectName("menubar")
        self.menuFile = QtWidgets.QMenu(self.menubar)
        self.menuFile.setObjectName("menuFile")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)
        self.actionImport = QtWidgets.QAction(MainWindow)
        self.actionImport.setObjectName("actionImport")
        self.actionExit = QtWidgets.QAction(MainWindow)
        self.actionExit.setObjectName("actionExit")
        self.menuFile.addAction(self.actionImport)
        self.menuFile.addAction(self.actionExit)
        self.menubar.addAction(self.menuFile.menuAction())

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.menuFile.setTitle(_translate("MainWindow", "File"))
        self.actionImport.setText(_translate("MainWindow", "Import"))
        self.actionExit.setText(_translate("MainWindow", "Exit"))


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

如果我尝试在Pycharm中运行此代码，它也只显示第一个菜单