code: @UiThread
      @NonNull
      @Override
      public HorizontalChildViewHolder onCreateChildViewHolder(@NonNull ViewGroup parent, int viewType) {
          View view = mInflater.inflate(R.layout.list_item_child_horizontal, parent, false);
          return new HorizontalChildViewHolder(view);
      }
docs: OnCreateViewHolder implementation for child items. The desired ChildViewHolder should
  be inflated here
  
  @param parent for inflating the View
  @return the user's custom parent ViewHolder that must extend ParentViewHolder