code: @Override
      public long getItemId(int position) {
          if(position > RecyclerView.NO_ID && position < getItemCount()) {
              M item = getItem(position);
              if (item != null) return item.hashCode();
              return position;
          }
          return RecyclerView.NO_ID;
      }
docs: Get the item Id for a given position
  @param position
  @return