  // MARK: UIViewControllerTransitioningDelegate protocol methods  // return the animataor when presenting a viewcontroller func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {     return self }  // return the animator used when dismissing from a viewcontroller func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {     return self }  