A Widget is not updated

I am having a hard time to find why the widget is not updated in my project.
Because the project is too big to upload in this post, I made a simplified code.
Code:
from PyQt5 import QtCore, QtGui, QtWidgets
class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(191, 223)
        self.verticalLayoutWidget = QtWidgets.QWidget(Form)
        self.verticalLayoutWidget.setGeometry(QtCore.QRect(0, 170, 191, 21))
        self.verticalLayoutWidget.setObjectName("verticalLayoutWidget")
        self.verticalLayout = QtWidgets.QVBoxLayout(self.verticalLayoutWidget)
        self.verticalLayout.setContentsMargins(55, 0, 55, 0)
        self.verticalLayout.setObjectName("verticalLayout")
        self.saveButton = QtWidgets.QPushButton(self.verticalLayoutWidget)
        self.saveButton.setStyleSheet("background-color: rgb(200, 200, 200)")
        self.saveButton.setFlat(False)
        self.saveButton.setObjectName("saveButton")
        self.verticalLayout.addWidget(self.saveButton)
        self.layoutWidget = QtWidgets.QWidget(Form)
        self.layoutWidget.setGeometry(QtCore.QRect(0, 20, 191, 22))
        self.layoutWidget.setObjectName("layoutWidget")
        self.threadcountLayout = QtWidgets.QHBoxLayout(self.layoutWidget)
        self.threadcountLayout.setContentsMargins(5, 0, 0, 0)
        self.threadcountLayout.setObjectName("threadcountLayout")
        self.label = QtWidgets.QLabel(self.layoutWidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label.sizePolicy().hasHeightForWidth())
        self.label.setSizePolicy(sizePolicy)
        self.label.setObjectName("label")
        self.threadcountLayout.addWidget(self.label)
        self.threadcountLineEdit = QtWidgets.QLineEdit(self.layoutWidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Fixed, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.threadcountLineEdit.sizePolicy().hasHeightForWidth())
        self.threadcountLineEdit.setSizePolicy(sizePolicy)
        self.threadcountLineEdit.setMinimumSize(QtCore.QSize(25, 20))
        self.threadcountLineEdit.setMaximumSize(QtCore.QSize(1, 20))
        self.threadcountLineEdit.setMaxLength(3)
        self.threadcountLineEdit.setObjectName("threadcountLineEdit")
        self.threadcountLayout.addWidget(self.threadcountLineEdit)
        self.label_2 = QtWidgets.QLabel(self.layoutWidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label_2.sizePolicy().hasHeightForWidth())
        self.label_2.setSizePolicy(sizePolicy)
        self.label_2.setObjectName("label_2")
        self.threadcountLayout.addWidget(self.label_2)
        self.retranslateUi(Form)
        QtCore.QMetaObject.connectSlotsByName(Form)
 
    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "Form"))
        self.saveButton.setText(_translate("Form", "save"))
        self.label.setText(_translate("Form", "HTTP thread count"))
        self.threadcountLineEdit.setText(_translate("Form", "0"))
        self.label_2.setText(_translate("Form", "s"))
 
 
class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(331, 351)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Fixed, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(MainWindow.sizePolicy().hasHeightForWidth())
        MainWindow.setSizePolicy(sizePolicy)
        MainWindow.setMinimumSize(QtCore.QSize(331, 351))
        MainWindow.setMaximumSize(QtCore.QSize(331, 351))
        MainWindow.setStyleSheet("background-color:rgb(250, 255, 151)")
 
 
if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    ui = Ui_Form()
    ui.setupUi(MainWindow)
    sys.exit(app.exec_())
setupUi function of Ui_MainWindow is properly applied, but the one of Ui_Form is not applied.
How can I solve this problem?