import sys

from PySide6 import QtGui, QtCore, QtWidgets

class TestWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super(TestWindow, self).__init__()

        self.setWindowTitle("TestTreeView")        

    def setWidget(self, widget):
        self.setCentralWidget(widget)

def loadStyleSheet(qssFile: str) -> str:
    qssData = None
    with open(qssFile, mode="rt", encoding="utf-8") as f:
        qssData = f.read()
    return qssData

if (__name__ == "__main__"):
    app = QtWidgets.QApplication(sys.argv)
    app.setStyleSheet(loadStyleSheet("stylesheet.qss"))
    
    dialog = TestWindow()
    dialog.show()

    test = QtWidgets.QPushButton("TestToopTip-Button")    
    test.setToolTip("TestToolTip")
    dialog.setWidget(test)    

    sys.exit(app.exec())