docs: @Override
      public List<V> returnCollectionItemsWithState(final List<Integer> states) {
          if (states == null) throw new IllegalArgumentException("states cannot be null");
  
          final List<V> retValue = new ArrayList<V>();
  
          for (final V item : getItems()) {
              if (states.contains(item.getState())) retValue.add(item);
          }
  
          return retValue;
      }