PySide2 subwindow

subwindow.py

from PySide2.QtWidgets import QApplication, QMainWindow, QMdiArea, QAction, QMdiSubWindow, QTextEdit
import sys
 
 
 
class MDIWindow(QMainWindow):
 
    count = 0
    def __init__(self):
        super().__init__()
 
        self.mdi = QMdiArea()
        self.setCentralWidget(self.mdi)
        bar = self.menuBar()
 
        file = bar.addMenu("File")
        file.addAction("New")
        file.addAction("cascade")
        file.addAction("Tiled")
        file.triggered[QAction].connect(self.WindowTrig)
        self.setWindowTitle("MDI Application")
 
    def WindowTrig(self, p):
 
 
        if p.text() == "New":
            MDIWindow.count = MDIWindow.count + 1
            sub = QMdiSubWindow()
            sub.setWidget(QTextEdit())
            sub.setWindowTitle("Sub Window" + str(MDIWindow.count))
            self.mdi.addSubWindow(sub)
            sub.show()
 
        if p.text() == "cascade":
            self.mdi.cascadeSubWindows()
 
        if p.text() == "Tiled":
            self.mdi.tileSubWindows()
 
app = QApplication(sys.argv)
mdi  =MDIWindow()
mdi.show()
app.exec_()