'Schedule delayed update.'

@callback
def _schedule_update(self):

    if self._update_scheduled:
        return
    @callback
    def do_update():
        'Really    update.'
        self.hass.async_add_job(self.async_update_ha_state)
        self._update_scheduled = False
    self._update_scheduled = True
    self.hass.loop.call_later(0.1, do_update)
