如何将QWidget参数传递给类

我正在学习PyQt5，我正在尝试创建一个消息框，但它不断给我错误

Traceback (most recent call last):
  File "addition_code_main.py", line 47, in clickMethod
    QMessageBox.about(self, "Title", "Message")
TypeError: about(QWidget, str, str): argument 1 has unexpected type 'MainWindow_EXEC'

我有下面的代码，我不明白我做错了什么，在哪里传递此Qwidget参数，

import sys

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import QApplication, QDialog, QPushButton, QMessageBox

from addition_code import Ui_MainWindow


class MainWindow_EXEC():

    def __init__(self):
        app = QtWidgets.QApplication(sys.argv)

        MainWindow = QtWidgets.QMainWindow()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(MainWindow)
        self.connect_singals()

        MainWindow.show()

        sys.exit(app.exec_())

    def connect_singals(self):
        self.ui.pushButton_3.clicked.connect(self.clickMethod)

    def clickMethod(self):
        QMessageBox.about(self, "Title", "Message")


if __name__ == "__main__":
    MainWindow_EXEC()

annex_code.py

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

# Form implementation generated from reading ui file 'addition_code.ui'
#
# Created by: PyQt5 UI code generator 5.13.0
#
# 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")
        self.lineEdit = QtWidgets.QLineEdit(self.centralwidget)
        self.lineEdit.setGeometry(QtCore.QRect(150, 40, 113, 20))
        self.lineEdit.setObjectName("lineEdit")
        self.lineEdit_2 = QtWidgets.QLineEdit(self.centralwidget)
        self.lineEdit_2.setGeometry(QtCore.QRect(430, 40, 113, 20))
        self.lineEdit_2.setObjectName("lineEdit_2")
        self.lineEdit_3 = QtWidgets.QLineEdit(self.centralwidget)
        self.lineEdit_3.setGeometry(QtCore.QRect(290, 40, 113, 20))
        self.lineEdit_3.setObjectName("lineEdit_3")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(260, 100, 81, 23))
        self.pushButton.setObjectName("pushButton")
        self.pushButton_2 = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton_2.setGeometry(QtCore.QRect(400, 110, 75, 23))
        self.pushButton_2.setObjectName("pushButton_2")
        self.pushButton_3 = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton_3.setGeometry(QtCore.QRect(250, 190, 75, 23))
        self.pushButton_3.setObjectName("pushButton_3")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

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

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "Addtion"))
        self.pushButton_2.setText(_translate("MainWindow", "MysqlConnect"))
        self.pushButton_3.setText(_translate("MainWindow", "MessagesBox"))

问题来源：stackoverflow