code: public final void add(@NonNull final AbstractItem item) {
          Condition.INSTANCE.ensureNotNull(item, "The item may not be null");
          items.add(item);
  
          if (item instanceof Item && ((Item) item).getIcon() != null) {
              iconCount++;
          } else if (item instanceof Divider) {
              dividerCount++;
          }
  
          rawItems = null;
          notifyOnDataSetChanged();
      }
docs: Adds a new item to the adapter.
  
  @param item
  The item, which should be added, as an instance of the class {@link AbstractItem}.
  The item may not be null