code: func DeviceSessionExists(p *redis.Pool, devEUI lorawan.EUI64) (bool, error) {
  	c := p.Get()
  	defer c.Close()
  
  	r, err := redis.Int(c.Do("EXISTS", fmt.Sprintf(deviceSessionKeyTempl, devEUI)))
  	if err != nil {
  		return false, errors.Wrap(err, "get exists error")
  	}
  	if r == 1 {
  		return true, nil
  	}
  	return false, nil
  }
docs: // DeviceSessionExists returns a bool indicating if a device session exist.