pyslots 装饰器的作用

显式地指出槽函数，可以加快运行速度

扩展阅读https://stackoverflow.com/questions/14421897/is-the-pyside-slot-decorator-necessary/14431607#14431607

https://pyqt.readthedocs.io/en/latest/signals_slots.html#the-pyqtslot-decorator