'Get the latest data and updates the states.'

@asyncio.coroutine
def async_update(self):

    sensor_values = [self.states[k] for k in self._entity_ids if (k in self.states)]
    self.min_value = calc_min(sensor_values)
    self.max_value = calc_max(sensor_values)
    self.mean = calc_mean(sensor_values, self._round_digits)
