'Called when a screen is added or screen configuration is changed (via xrandr)
Common usage is simply to call ``qtile.cmd_restart()`` on each event
(to restart qtile when there is a new monitor):
**Arguments**
* qtile manager instance
* ``xproto.randr.ScreenChangeNotify`` event
Examples
@libqtile.hook.subscribe.screen_change
def restart_on_randr(qtile, ev):
qtile.cmd_restart()'

def screen_change(self, func):

    return self._subscribe('screen_change', func)
