def METHOD_NAME(self, event):
    if event.button() == Qt.LeftButton:
        clickedRect = self._optionsRects[self._clickedIndex]
        if QRect(*clickedRect).contains(event.pos()):
            self._selection = {self._clickedIndex}
            if (
                self._selectionMode > 1
                and QApplication.keyboardModifiers() & Qt.ShiftModifier
            ):
                shiftSelection = self._selection ^ self._oldSelection
                if shiftSelection:
                    self._selection = shiftSelection
            self.clicked.emit()
        else:
            self._selection = self._oldSelection
        self.update()
        del self._clickedIndex
        del self._oldSelection
    else:
        super().METHOD_NAME(event)