关于pyside2在pycharm中运行出错 app = QApplication(sys.argv) TypeError: 'NoneType' object is not callable？

在pycharm中运行这段报错：

import sys
from PySide2.QtWidgets import QApplication, QLabel
print(sys.argv)
app = QApplication.instance()
if app == None:
    app = QApplication(sys.argv)

# QLabel组件用于显示文本
label = QLabel("<font color=red size=40>Hello World!</font>")
label.show()
app.exec_()

Traceback (most recent call last):
  File "E:/工作/copy2/Test.py", line 7, in <module>
    app = QApplication(sys.argv)
TypeError: 'NoneType' object is not callable

但是在python编译器里面就不会报错，求指点？