问Python如何从QDialog中打开弹出的QMainWindow

EN

def button_click():
    dialog = QtGui.QMessageBox.information(self, 'Delete?', 'Are you sure you want to delete this item?', buttons = QtGui.QMessageBox.Ok|QtGui.QMessageBox.Cancel)

from PyQt4 import QtCore, QtGui
from mainwindow_ui import Ui_MainWindow

class MainWindow(QtGui.QMainWindow, Ui_MainWindow):
    def __init__(self):
        QtGui.QMainWindow.__init__(self)
        self.setupUi(self)
        self.buttonDelete.clicked.connect(self.handleButtonDelete)

    def handleButtonDelete(self):
        answer = QtGui.QMessageBox.question(
            self, 'Delete Item', 'Are you sure you want to delete this item?',
            QtGui.QMessageBox.Yes | QtGui.QMessageBox.No |
            QtGui.QMessageBox.Cancel,
            QtGui.QMessageBox.No)
        if answer == QtGui.QMessageBox.Yes:
            # code to delete the item
            print('Yes')
        elif answer == QtGui.QMessageBox.No:
            # code to carry on without deleting
            print('No')
        else:
            # code to abort the whole operation
            print('Cancel')

if __name__ == '__main__':

    import sys
    app = QtGui.QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

TypeError: question(QWidget, str, str, buttons: Union[QMessageBox.StandardButtons, QMessageBox.StandardButton] = QMessageBox.StandardButtons(QMessageBox.Yes|QMessageBox.No), defaultButton: QMessageBox.StandardButton = QMessageBox.NoButton): argument 1 has unexpected type 'Ui_MainWindow'

def handleButtonDelete(self):
    answer = QtGui.QMessageBox.question(
        None, 'Delete Item', 'Are you sure you want to delete this item?',
        QtGui.QMessageBox.Yes | QtGui.QMessageBox.No |
        QtGui.QMessageBox.Cancel,
        QtGui.QMessageBox.No)
    if answer == QtGui.QMessageBox.Yes:
        # code to delete the item
        print('Yes')
    elif answer == QtGui.QMessageBox.No:
        # code to carry on without deleting
        print('No')
    else:
        # code to abort the whole operation
        print('Cancel')