         }
         addChild(buttonContainer)
         view.addAutolayoutSubview(buttonContainer.view)
-        bottomConstraint = buttonContainer.view.bottomAnchor.constraint(equalTo: view.bottomAnchor)
 
         NSLayoutConstraint.activate([
             containedViewController.view.topAnchor.constraint(equalTo: view.topAnchor),

            containedViewController.view.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            buttonContainer.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            buttonContainer.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            bottomConstraint,
            ])
        containedViewController.didMove(toParent: self)
        buttonContainer.didMove(toParent: self)

    }
    private let bottomViewKind: BottomViewKind
    private var buttonContainer: UIViewController!
    
    private enum BottomViewKind {
        case button(UIButton, UIEdgeInsets)
