Control focused index path after fast scrolling

Hello,
Is it a way how we can control what index path will be focused after fast scrolling ends?
e.g. User scrolls in 3rd column and when he enter the fast scrolling it should focus item in 3rd column when he ends.
I implemented these

UICollectionViewDataSource functions:
1. func indexTitles(for: UICollectionView) -> [String]?
2. func collectionView(UICollectionView, indexPathForIndexTitle: String, at: Int) -> IndexPath


Indexes are shown as expected. But it doesn't matter what IndexPath is returned in #2, it always focus first column. What is this function used for if not for control of focus?