Не работает QGridLayout главного окна после конвертации из .ui в .py, как исправить?

Не работает QGridLayout главного окна после конвертации из .ui в .py, как исправить?

ссылка на .ui файл: https://drive.google.com/file/d/1dO7XXql5OPxL8mc-bUM_ZnjaNc34Ybm9/view?usp=sharing

1. В Qt Designer все нормально отображается, динамически изменяется

2. После конвертации из .ui в .py, все находится в правом верхнем углу и никак не менятся

3. Код:

   from PyQt5 import QtCore, QtGui, QtWidgets
    from PyQt5.QtWidgets import QMainWindow
    import sys
   
    class Ui_Dialog(object):
        def setupUi(self, Dialog):
            Dialog.setObjectName("Dialog")
            Dialog.resize(569, 449)
            self.gridLayout_2 = QtWidgets.QGridLayout(Dialog)
            self.gridLayout_2.setObjectName("gridLayout_2")
            self.verticalLayout_2 = QtWidgets.QVBoxLayout()
            self.verticalLayout_2.setObjectName("verticalLayout_2")
            self.horizontalLayout = QtWidgets.QHBoxLayout()
            self.horizontalLayout.setObjectName("horizontalLayout")
            spacerItem = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Minimum)
            self.horizontalLayout.addItem(spacerItem)
            self.pushButton = QtWidgets.QPushButton(Dialog)
            self.pushButton.setObjectName("pushButton")
            self.horizontalLayout.addWidget(self.pushButton)
            spacerItem1 = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Minimum)
            self.horizontalLayout.addItem(spacerItem1)
            self.verticalLayout_2.addLayout(self.horizontalLayout)
            self.stackedWidget = QtWidgets.QStackedWidget(Dialog)
            self.stackedWidget.setObjectName("stackedWidget")
            self.page = QtWidgets.QWidget()
            self.page.setObjectName("page")
            self.gridLayout = QtWidgets.QGridLayout(self.page)
            self.gridLayout.setObjectName("gridLayout")
            self.verticalLayout = QtWidgets.QVBoxLayout()
            self.verticalLayout.setObjectName("verticalLayout")
            spacerItem2 = QtWidgets.QSpacerItem(20, 40, QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Expanding)
            self.verticalLayout.addItem(spacerItem2)
            self.horizontalLayout_3 = QtWidgets.QHBoxLayout()
            self.horizontalLayout_3.setObjectName("horizontalLayout_3")
            spacerItem3 = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Minimum)
            self.horizontalLayout_3.addItem(spacerItem3)
            self.horizontalLayout_2 = QtWidgets.QHBoxLayout()
            self.horizontalLayout_2.setObjectName("horizontalLayout_2")
            self.pushButton_2 = QtWidgets.QPushButton(self.page)
            self.pushButton_2.setObjectName("pushButton_2")
            self.horizontalLayout_2.addWidget(self.pushButton_2)
            self.pushButton_3 = QtWidgets.QPushButton(self.page)
            self.pushButton_3.setObjectName("pushButton_3")
            self.horizontalLayout_2.addWidget(self.pushButton_3)
            self.horizontalLayout_3.addLayout(self.horizontalLayout_2)
            spacerItem4 = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Minimum)
            self.horizontalLayout_3.addItem(spacerItem4)
            self.verticalLayout.addLayout(self.horizontalLayout_3)
            spacerItem5 = QtWidgets.QSpacerItem(20, 40, QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Expanding)
            self.verticalLayout.addItem(spacerItem5)
            self.gridLayout.addLayout(self.verticalLayout, 0, 0, 1, 1)
            self.stackedWidget.addWidget(self.page)
            self.page_2 = QtWidgets.QWidget()
            self.page_2.setObjectName("page_2")
            self.stackedWidget.addWidget(self.page_2)
            self.verticalLayout_2.addWidget(self.stackedWidget)
            self.gridLayout_2.addLayout(self.verticalLayout_2, 0, 0, 1, 1)
   
            self.retranslateUi(Dialog)
            QtCore.QMetaObject.connectSlotsByName(Dialog)
   
            self.show()
   
        def retranslateUi(self, Dialog):
            _translate = QtCore.QCoreApplication.translate
            Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
            self.pushButton.setText(_translate("Dialog", "PushButton"))
            self.pushButton_2.setText(_translate("Dialog", "PushButton"))
            self.pushButton_3.setText(_translate("Dialog", "PushButton"))
   
   
    class MainWindow(QMainWindow, untitled.Ui_Dialog):
        def __init__(self):
            super().__init__()
            self.setupUi(self)
   
   
   
    if __name__ == '__main__':
        app = QtWidgets.QApplication(sys.argv)
        w = MainWindow()
        sys.exit(app.exec_())