DecorationViewsHandlerUpdates.swift

override func prepare(forCollectionViewUpdates updateItems: [UICollectionViewUpdateItem]) {
    super.prepare(forCollectionViewUpdates: updateItems)
    decorationViewHandler.prepare(forCollectionViewUpdates: updateItems)
}

override func indexPathsToInsertForDecorationView(ofKind elementKind: String) -> [IndexPath] {
    return decorationViewHandler.inserted(for: elementKind)
}

override func indexPathsToDeleteForDecorationView(ofKind elementKind: String) -> [IndexPath] {
    return decorationViewHandler.deleted(for: elementKind)
}