code: @Nullable
      public Item getItem(RecyclerView.ViewHolder viewHolder) {
          FastAdapter<Item> adapter = getFastAdapter(viewHolder);
          if (adapter == null) {
              return null;
          }
          //we get the adapterPosition from the viewHolder
          int pos = adapter.getHolderAdapterPosition(viewHolder);
          //make sure the click was done on a valid item
          if (pos != RecyclerView.NO_POSITION) {
              //we update our item with the changed property
              return adapter.getItem(pos);
          }
          return null;
      }
docs: helper method to get the item for this ViewHolder
  
  @param viewHolder
  @return