What is the proper way to copy layer references into presentation layer?

I have MyLayer and it has a sublayer that it also holds a reference to. In that setup what is the proper way to override init(layer: Any)?

Right now I'm doing it like this ... layer.mySublayer.presentation()! is that correct? Is that always going to work, or will presentation ever be nil in this context?

Thanks for any tips!

class MyLayer: CALayer {

    var mySublayer: CALayer

    public override init() {
        mySublayer = CALayer()
        super.init()
        addSublayer(mySublayer)
    }

    override init(layer: Any) {
        let layer = layer as! MyLayer
        mySublayer = layer.mySublayer.presentation()!
        super.init(layer: layer)
    }

    required init?(coder: NSCoder) {
        fatalError("has not been implemented")
    }

}