code: public boolean addItems(Collection<T> items) {
          if (items.isEmpty()) return false;
          int previousSize = getItemCount();
          if (mListItems.addAll(items)) {
              notifyItemRangeInserted(previousSize, items.size());
              return true;
          }
          return false;
      }
docs: Append a collection of items and refresh the {@code RecyclerView} by calling
  {@code notifyItemRangeInserted()}.
  
  @param items collection of items to append
  @return true if any data was modified by this operation, false otherwise.