code: public void appendGroup(@Nullable List<L> cards) {
          if (cards == null || cards.size() == 0)
              return;
  
          createSnapshot();
  
          final List<LayoutHelper> helpers = new LinkedList<>(getLayoutHelpers());
  
          mCards.ensureCapacity(mCards.size() + cards.size());
  
          helpers.addAll(transformCards(cards, mData, mCards));
  
          setLayoutHelpers(helpers);
  
          diffWithSnapshot();
  
          // not use {@link notifyItemRangeChanged} because not sure whether animations is required
          // notifyItemRangeChanged(oldItem, newitems);
          notifyDataSetChanged();
      }
docs: append new cards into adapter
  
  @param cards new cards will be added to the end