Updates the icon for this lock button based on its check state.

def updateState(self):
        """
        Updates the icon for this lock button based on its check state.
        """
        if self.isChecked():
            self.setIcon(self.lockIcon())
            self.setToolTip('Click to unlock')
        else:
            self.setIcon(self.unlockIcon())
            self.setToolTip('Click to lock')