async def async_added_to_hass(self):
    'Subscribe device events.'
    self.async_on_remove(async_dispatcher_connect(self.hass, self.device.signal_reachable, self.update_callback))
Subscribe device events.
async def async_added_to_hass(self):
    
    self.async_on_remove(async_dispatcher_connect(self.hass, self.device.signal_reachable, self.update_callback))