In the Chapter 9 Challenge: RecyclerView ViewTypes the reference docs for getItemViewType should be https://developer.android.com/reference/kotlin/androidx/recyclerview/widget/RecyclerView.Adapter#getitemviewtype
instead of http://developer.android.com/reference/android/support/v7/widget/RecyclerView.Adapter.html#getItemViewType
as the support library is deprecated as highlighted by @android77 here