code: public ModelAdapter<?, Item> set(int position, Item item) {
          if (mOriginalItems != null) {
              if (mItemAdapter.isUseIdDistributor()) {
                  mItemAdapter.getIdDistributor().checkId(item);
              }
              mOriginalItems.set(getAdapterPosition(mItemAdapter.getAdapterItems().get(position)) - mItemAdapter.getFastAdapter().getPreItemCount(position), item);
              publishResults(mConstraint, performFiltering(mConstraint));
              return mItemAdapter;
          } else {
              return mItemAdapter.setInternal(position, item);
          }
      }
docs: sets an item at the given position, overwriting the previous item
  
  @param position the global position
  @param item     the item to set