Returns an array of index paths for the supplementary views you want to add to the layout.
- iOS 7.0+
- tvOS 9.0+
The specific type of supplementary view.
An array of
NSIndex objects indicating the location of the new supplementary views or an empty array if you do not want to add any supplementary views.
The collection view calls this method whenever you add cells or sections to the collection view. Implementing this method gives your layout object an opportunity to add new supplementary views to complement the additions.