public static void Start()
        {
            vehicleCollection = new Collections(TYPES_PATH, VEHICLE_PATH, RENT_PATH);

            vehicleCollection.Print();
            vehicleCollection.Insert(-1, AddNewVehicle()); // add new vehicle
            vehicleCollection.Delete(1);
            vehicleCollection.Delete(4);
            Console.WriteLine("\nCollection after modify:");
            vehicleCollection.Print();
            vehicleCollection.Sort();
            Console.WriteLine("\nCollection after sort by model name:");
            vehicleCollection.Print();
        }