Cannot convert value of type 'Decoder.Protocol' to expected argument type 'NSCoder'

@IBOutlet weak var collectionView: UICollectionView!
@IBOutlet weak var totalLabel: UILabel!
@IBOutlet weak var balanceLabel: UILabel!
@IBOutlet weak var quantityLabel: UILabel!
@IBOutlet weak var priceLabel: UILabel!

let vendingMachine: VendingMachine

required init?(coder: NSCoder) {
    do {
        let dictionary = try PlistConverter.dictionary(fromFile: "VendingInventory", ofType: "plist")
        let inventory = try InventoryUnarchiver.vendingInventory(formDictionary: dictionary)
        self.vendingMachine = FoodVendingMachine(inventory: inventory)
    } catch let error {
        fatalError("\(error)")
    }
    // Problem - ved ikke hvad aDecoder er? Video giver ikke svar.
    super.init(coder: aDecoder)
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    setupCollectionViewCells()
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

// MARK: - Setup

func setupCollectionViewCells() {
    let layout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 20, right: 0)

    let padding: CGFloat = 10
    let itemWidth = screenWidth/3 - padding
    let itemHeight = screenWidth/3 - padding

    layout.itemSize = CGSize(width: itemWidth, height: itemHeight)
    layout.minimumLineSpacing = 10
    layout.minimumInteritemSpacing = 10

    collectionView.collectionViewLayout = layout
}

// MARK: UICollectionViewDataSource

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 12
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as? VendingItemCell else { fatalError() }

    return cell
}

// MARK: - UICollectionViewDelegate

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    updateCell(having: indexPath, selected: true)
}

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    updateCell(having: indexPath, selected: false)
}

func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath) {
    updateCell(having: indexPath, selected: true)
}

func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath) {
    updateCell(having: indexPath, selected: false)
}

func updateCell(having indexPath: IndexPath, selected: Bool) {

    let selectedBackgroundColor = UIColor(red: 41/255.0, green: 211/255.0, blue: 241/255.0, alpha: 1.0)
    let defaultBackgroundColor = UIColor(red: 27/255.0, green: 32/255.0, blue: 36/255.0, alpha: 1.0)

    if let cell = collectionView.cellForItem(at: indexPath) {
        cell.contentView.backgroundColor = selected ? selectedBackgroundColor : defaultBackgroundColor
    }
}