Ошибка наследования

Почему ошибка? Класс AddWords.

Ошибка: TypeError: Cannot create a consistent method resolution order (MRO) for bases QMainWindow, MainWindow

import PyQt5
from PyQt5 import QtCore, QtWidgets, QtGui
from PyQt5.QtWidgets import QApplication, QWidget, QDesktopWidget, QMainWindow, QAction, qApp
from PyQt5.QtGui import QIcon
from PyQt5.QtCore import QTimer
import sqlite3
import random

HEIGHT = 750
WIDTH = 1300
class Menu(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.menubar = parent.menuBar()
        self.file = self.menubar.addMenu('&Опции')
        self.exitAction = QAction(QIcon('icons/cross-exit.ico'), '&Exit', self)
        self.exitAction.setShortcut('Ctrl+Q')
        self.exitAction.setStatusTip('Exit application')
        self.exitAction.triggered.connect(parent.close)
        self.file.addAction(self.exitAction)

    def addMenu(self, text, command, icon, shortcut=None, statusTip=None) :
        actionName = QAction(QIcon(icon), text, self)
        if shortcut:
            actionName.setShortcut(shortcut)
        if statusTip:
            actionName.setStatusTip(statusTip)
        actionName.triggered.connect(command)

        self.file.insertAction(self.exitAction, actionName)

    def addNestedMenu(self, text, text2, text3, command, command2, icon, icon2):
        words = self.file.addMenu(text)
        action = QAction(QIcon(icon), text2, self)
        action2 = QAction(QIcon(icon2), text3, self)
        action.triggered.connect(command)
        action2.triggered.connect(command2)
        words.addAction(action)
        words.addAction(action2)
        self.file.addAction(self.exitAction)


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

    def initUI(self):
        def stylingsCss(self):
            self.label.setStyleSheet("""
                QLabel{
                    background-color: #E0FFFF;
                    border-radius: 25px;
                }

            """)
            self.labelAnswer.setStyleSheet("""
                QLabel{
                    background-color: #E0FFFF;
                    border-radius: 25px;
                }

            """)
            self.labelEdit.setStyleSheet("background-color: #7FFFD4; border: none; border-radius: 25px;")
            self.countLabel.setStyleSheet("""
                QLabel{
                    font-size: 15px;
                    border-radius: 25px;
                    min-height: 50px;
                    max-height: 50px;
                    min-width: 50px;
                    max-width: 50px;
                    background-color: #FAF0E6;
                    border: 1px double #ADD8E6;
                }
                QToolTip { 
                    background-color: #ffffff; 
                    border: 1px solid green; 
                }
            """)
            self.courseButton.setStyleSheet("""
                    font-size: 15px;
                    border-radius: 15px;
                    min-height: 40px;
                    max-height: 40px;
                    min-width: 100px;
                    max-width: 50px;
                    background-color: #ADD8E6;
                    border: 1px double #90EE90;
                """)
            self.wordButton.setStyleSheet("""
                QPushButton {
                    font-size: 15px;
                    border-radius: 15px;
                    min-height: 40px;
                    max-height: 40px;
                    min-width: 100px;
                    max-width: 50px;
                    background-color: #ADD8E6;
                    border: 1px double #90EE90;
                }

                QPushButton:hover:pressed {
                    background-color: green;
                }
                QPushButton:hover:!pressed {
                    background-color: yellow;
                }
                QToolTip { 
                    background-color: #ffffff; 
                    border: 1px solid green; 
                }
                """)

        def answerCheckerRus(self):
            self.labelAnswer.setStyleSheet("""
                background-color: #E0FFFF;
            """)
            self.labelAnswer.setText("")
            self.labelEdit.setText("")
            self.countLabel.setStyleSheet("""
                QLabel{
                    font-size: 15px;
                    border-radius: 25px;
                    min-height: 50px;
                    max-height: 50px;
                    min-width: 50px;
                    max-width: 50px;
                    background-color: #FAF0E6;
                    border: 1px double #ADD8E6;
                }
                QToolTip { 
                    background-color: #ffffff; 
                    border: 1px solid green; 
                }
            """)
            if self.toggle == 1:
                sqlLiteConnect(self, 'db/Lings_Words_Db.db', 'generalWords', 'Word', 'rus')


        def answerCheckerEng(self):
            self.labelAnswer.setStyleSheet("""
                background-color: #E0FFFF;
            """)
            self.labelAnswer.setText("")
            self.labelEdit.setText("")
            self.countLabel.setStyleSheet("""
                QLabel{
                    font-size: 15px;
                    border-radius: 25px;
                    min-height: 50px;
                    max-height: 50px;
                    min-width: 50px;
                    max-width: 50px;
                    background-color: #FAF0E6;
                    border: 1px double #ADD8E6;
                }
                QToolTip { 
                    background-color: #ffffff; 
                    border: 1px solid green; 
                }
            """)
            if self.toggle == 1:
                sqlLiteConnect(self, 'db/Lings_Words_Db.db', 'generalWords', 'Word', 'eng')
        def binderAnswerCheckerRus(self):           # Связывание фуйкции answerCheckerRus через 1.5сек
            QTimer.singleShot(1500, lambda: answerCheckerRus(self))

        def binderAnswerCheckerEng(self):           # Связывание фуйкции answerCheckerEng через 1.5сек
            QTimer.singleShot(1500, lambda: answerCheckerEng(self))

        def sqlLiteConnect(self, db, table, column_name, lang='eng'):         #Подключение к БД + запись слов в лейбл
            self.lang = lang
            self.connect = sqlite3.connect(db)
            self.cursor = self.connect.cursor()
            self.query_columns = f"PRAGMA table_info('{table}')"
            self.cursor.execute(self.query_columns)

            self.queryRow = f"""SELECT id, Word, Translation FROM {table} WHERE id=?"""
            self.cursor.execute(self.queryRow, (random.randint(0, 2000),))
            self.text_db = self.cursor.fetchone()
            if lang == 'eng':
                self.label.setText(self.text_db[1].title())
            else: 
                self.label.setText(self.text_db[2].title())

        def checker(self):              # Проверка на язык + выполнение функции answerChecker через 1500 мс 
            self.text_in_LabelEdit = self.labelEdit.text()
            if self.lang == 'eng':
                if self.text_in_LabelEdit == self.text_db[2]:
                    self.toggle = 1
                    self.labelAnswer.setStyleSheet('background-color: #90ff77; border-radius: 25px;')
                    self.labelAnswer.setText("Верно")
                    binderAnswerCheckerEng(self)
                    xCounter(self)
                else: 
                    self.toggle = 0
                    self.labelAnswer.setStyleSheet('background-color: #ff4040; border-radius: 25px;')
                    self.labelAnswer.setText(self.text_db[2])
                    binderAnswerCheckerEng(self)
                    self.var = 0
                    self.countLabel.setText("0")
                    self.countLabel.setStyleSheet("""
                        QLabel{
                            font: 20px Arial, bold;
                            border-radius: 25px;
                            min-height: 50px;
                            max-height: 50px;
                            min-width: 50px;
                            max-width: 50px;
                            background-color: #ff4040;
                            border: 1px solid black;
                        }
                        QToolTip { 
                            background-color: #ffffff; 
                            border: 1px solid green; 
                        }
                    """)

            else:
                if self.text_in_LabelEdit == self.text_db[1]:
                    self.toggle = 1
                    self.labelAnswer.setStyleSheet('background-color: #90ff77; border-radius: 25px;')
                    self.labelAnswer.setText("Верно")
                    binderAnswerCheckerRus(self)
                    xCounter(self)
                else: 
                    self.toggle = 0
                    self.labelAnswer.setStyleSheet('background-color: #ff4040; border-radius: 25px;')
                    self.labelAnswer.setText(self.text_db[1])
                    binderAnswerCheckerRus(self)
                    self.var = 0
                    self.countLabel.setText("0")

        def wordButtonToggler(self):            #Переключение между языками
            self.text_in_wordButton = self.wordButton.text()
            self.labelEdit.setFocus()
            if self.text_in_wordButton == 'EN':
                self.wordButton.setText("RU")
                sqlLiteConnect(self, 'db/Lings_Words_Db.db', 'generalWords', 'Word', 'rus')
            else: 
                self.wordButton.setText("EN")
                sqlLiteConnect(self, 'db/Lings_Words_Db.db', 'generalWords', 'Word', 'eng')

        def xCounter(self):
            self.var += 1
            self.countLabel.setText(str(self.var))
            self.countLabel.setStyleSheet("""
                QLabel{
                    font: 20px Arial, bold;
                    border-radius: 25px;
                    min-height: 50px;
                    max-height: 50px;
                    min-width: 50px;
                    max-width: 50px;
                    background-color: #90ff77;
                    border: 1px solid black;
                }
                QToolTip { 
                    background-color: #ffffff; 
                    border: 1px solid green; 
                }
            """)

        self.var = 0
        self.q = QDesktopWidget().availableGeometry()
        self.r_w, self.r_h = self.q.width(), self.q.height()
        self.setGeometry(self.r_w/2-WIDTH/2, self.r_h/2-HEIGHT/2, WIDTH, HEIGHT)
        self.w = self.size().width()
        self.h = self.size().height()
        self.setFixedSize(1300, 750)
        self.setWindowTitle('Lings')
        self.setWindowIcon(QIcon('icons/Lings.ico'))
        self.label = QtWidgets.QLabel("sdsd", self)
        self.labelAnswer = QtWidgets.QLabel(self)
        self.labelEdit = QtWidgets.QLineEdit(self)
        self.countLabel = QtWidgets.QLabel('0', self)
        self.courseButton = QtWidgets.QPushButton('Общий курс', self)
        self.wordButton = QtWidgets.QPushButton('EN', self)
        self.l_w, self.l_h = 500, 100
        self.label.setAlignment(QtCore.Qt.AlignCenter)
        self.countLabel.setAlignment(QtCore.Qt.AlignCenter)
        self.labelAnswer.setAlignment(QtCore.Qt.AlignCenter)
        self.labelEdit.setAlignment(QtCore.Qt.AlignCenter)
        self.labelAnswer.resize(self.l_w, self.l_h)
        self.countLabel.resize(50, 50)
        self.courseButton.resize(100, 40)
        self.wordButton.resize(100, 40)
        self.labelEdit.resize(self.l_w, self.l_h)
        self.labelAnswer.move(self.w/2-self.l_w/2, 250)
        self.countLabel.move(self.w/2-self.l_w/2+550, 275)
        self.courseButton.move(self.w/2-self.l_w/2+750, 25)
        self.wordButton.move(self.w/2-self.l_w/2-350, 25)
        self.labelEdit.move(self.w/2-self.l_w/2, 400)
        self.label.setAlignment(QtCore.Qt.AlignCenter)
        self.label.resize(self.l_w, self.l_h)
        self.label.move(self.w/2-self.l_w/2, 100)
        self.label.setFont(QtGui.QFont('Verdana', 24))
        self.labelAnswer.setFont(QtGui.QFont('Verdana', 24))
        self.labelEdit.setFont(QtGui.QFont('Verdana', 24))
        self.countLabel.setToolTip("Ваша серия правильных ответов")
        self.wordButton.setToolTip("Изменение языка") 
        self.labelEdit.setFocus()
        self.labelEdit.returnPressed.connect(lambda: checker(self))
        self.wordButton.pressed.connect(lambda: wordButtonToggler(self))

        self.menu = Menu(self)
        self.menu.addNestedMenu('Свои слова', 'Добавить слова', 'Посмотреть список слов', lambda: AddWords(self), lambda: AddWords(self), 'icons/add.png', 'icons/test.ico')
        stylingsCss(self)
        sqlLiteConnect(self, 'db/Lings_Words_Db.db', 'generalWords', 'Word', 'eng')

        self.show()

class AddWords(QMainWindow, MainWindow):

    def __init__(self, parent=None):
        super().__init__(parent, QtCore.Qt.Window)
        self.initUI()
        parent.hide()

    def initUI(self):

        self.q = QDesktopWidget().availableGeometry()
        self.r_w, self.r_h = self.q.width(), self.q.height()
        self.w = self.size().width()
        self.h = self.size().height()
        self.l_w, self.l_h = 500, 100
        self.setGeometry(self.r_w/2-WIDTH/2, self.r_h/2-HEIGHT/2, WIDTH, HEIGHT)
        self.setFixedSize(800, 400)
        self.setWindowTitle('Lings2')
        self.setWindowIcon(QIcon('icons/Lings.ico'))
        self.lineEditAdd = QtWidgets.QLineEdit(self)
        self.lineEditAdd.setAlignment(QtCore.Qt.AlignCenter)
        self.lineEditAdd.resize(self.l_w, self.l_h)
        self.lineEditAdd.setFont(QtGui.QFont('Verdana', 24))
        self.lineEditAdd.move(self.w/2-self.l_w/2, 400)
        self.menu = Menu(self)

        self.show()

if __name__ == '__main__':
    app = QApplication(sys.argv)

    mainWindow = MainWindow()
    sys.exit(app.exec_())```