code: public void addNewItems(List<M> newItems) {
      if (this.items == null) {
        this.items = createEmptyList();
      }
  
      this.items.addAll(newItems);
    }
docs: <p>
  Add items.
  </p>
  
  <p>
  If {@link #items} is null an empty list of {@link M} will be created first.
  </p>
  
  @param newItems items