PYQT5 CSS SetSheetStyle嵌套写作

Question

最近，我得到了一个请求，通过在pyqt5中使用CSS来实现悬停效果，我不知道如何编写嵌套写作，现在显示我的代码：

import sys
from PyQt5.QtWidgets import QWidget, QPushButton, QApplication, QAction, QMenu
from PyQt5.QtGui import QPalette, QBrush, QPixmap


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()  

    def initUI(self):
        btn = QPushButton('button', self)

        button = QMenu()

        btn.setStyleSheet("QPushButton{color:black}"
                          "QPushButton:hover{color:red}"
                          "QPushButton{background-color:rgb(78,255,255)}"
                          "QPushButton{border:2px}"
                          "QPushButton{border-radius:10px}"
                          "QPushButton{padding:2px 4px}"
                          "QPushButton:hover{QMenu{display:block}}"
                          # "QMenu:!hover{display:block}"
                          # "#button:!hover{display:block}"
                          )

        # button.setStyleSheet("QMenu:!hover{display:None}")


        new_action = QAction("create", button)
      
        new_action.triggered.connect(lambda: print("file"))
        open_action = QAction("open", button)
        open_action.triggered.connect(lambda: print("open"))
        exit_action = QAction("quit", button)
        exit_action.triggered.connect(lambda: print("quit"))
        button.addAction(new_action)
        button.addAction(open_action)

        btn.setMenu(button)

        self.show()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())

“ qpushbutton：hover {qmenu {qmenu {display}}}}

这行没有效果，所以我想知道如何使这条线效果并获得正确的写作，谢谢！