Фоновая картинка PyQt

Как можно вставить картинку фоном. Нижеприведенный вариант кода не срабатывает

import sys
from PyQt5 import QtCore, QtGui, QtWidgets


class ClassesPage1(QtWidgets.QWizardPage):
    def __init__(self, *args, **kwargs):
        super(ClassesPage1, self).__init__(*args, **kwargs)

        self.setTitle("...")
        self.setSubTitle("...")

        self.checkBox_1 = QtWidgets.QCheckBox('...')
        self.checkBox_2 = QtWidgets.QCheckBox('...')
        self.checkBox_3 = QtWidgets.QCheckBox('...')
        self.checkBox_4 = QtWidgets.QCheckBox('...')

        self.layout = QtWidgets.QVBoxLayout()
        self.layout.addWidget(self.checkBox_1)
        self.layout.addWidget(self.checkBox_2)
        self.layout.addWidget(self.checkBox_3)
        self.layout.addWidget(self.checkBox_4)
        self.setLayout(self.layout)

        self.checkBox_1.stateChanged.connect(self.check)
        self.checkBox_2.stateChanged.connect(self.check)
        self.checkBox_3.stateChanged.connect(self.check)
        self.checkBox_4.stateChanged.connect(self.check)
        
        self.listCheckBox = [self.checkBox_1, self.checkBox_2, self.checkBox_3, self.checkBox_4] 
        self.a = 0                                                                                    

    def check(self, state):
        self.a = 0                                               
        if state == Qt.Checked:
            a = a + 1
        for checkBox in self.listCheckBox:                       
            if checkBox.isChecked():                              
                self.a += 1                                      
        print(self.a)

    def nextId(self):
        return Wizard.class4

stylesheet = '''
    QWidget {
        background-image: url("C:\111.jpg");
    }
'''
        
    if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)

    app.setStyleSheet(stylesheet)

    w = ClassesPage1()
    w.show()
    sys.exit(app.exec_())