public void AddAirConditioner(AirConditioner airConditioner)
        {
            var isDublicate =
                this.airConditioners.Any(
                    c => c.Model == airConditioner.Model);

            if (isDublicate)
            {
                throw new ArgumentException(Constants.Duplicate);
            }
            else
            {
                this.airConditioners.Add(airConditioner);
            }
        }
 public void RemoveAirConditioner(AirConditioner airConditioner)
 {
     this.airConditioners.Remove(airConditioner);
 }