code: public ModelAdapter<?, Item> add(List<Item> items) {
          if (mOriginalItems != null && items.size() > 0) {
              if (mItemAdapter.isUseIdDistributor()) {
                  mItemAdapter.getIdDistributor().checkIds(items);
              }
              mOriginalItems.addAll(items);
              publishResults(mConstraint, performFiltering(mConstraint));
              return mItemAdapter;
          } else {
              return mItemAdapter.addInternal(items);
          }
      }
docs: add a list of items to the end of the existing items
  will prior check if we are currently filtering
  
  @param items the items to add