from PySide6.QtCore import QTimer
from PySide6.QtWidgets import QApplication, QMessageBox

app = QApplication()

msg = 'Press "Yes"'
standard_buttons = QMessageBox.StandardButton
buttons = standard_buttons.Yes | standard_buttons.No
box = QMessageBox(QMessageBox.Question, 'Question', msg, buttons)

def accepted():
    print('Accepted!')

    # Now we will reject it later
    print('Now rejecting...')
    QTimer.singleShot(0, box.reject)

def rejected():
    print('Rejected!')

def finished():
    print('Finished!')

box.finished.connect(finished)
box.accepted.connect(accepted)
box.rejected.connect(rejected)

box.show()

app.exec()