Returns the child view controller that contains the source of the unwind segue.
- iOS 9.0+
- tvOS 9.0+
The unwind segue source object containing information about the unwind segue.
The view controller that contains the segue source.
Container view controllers call this method to identify the child view controller that is the source of the unwind segue. Typically, you call this method from your
allowed method so that you can remove the corresponding view controller from the returned list of children.