    open func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        guard let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from),
            let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
            else { return }
        
        let containerView = transitionContext.containerView
        
        if forwardTransition {
            containerView.addSubview(toVC.view)