anchor.diff:  
     int indexOf(element, [int start = 0]) => _srcList.indexOf(element, start);
     int lastIndexOf(element, [int start]) => _srcList.lastIndexOf(element, start);
  -  void insert(int index,  element) => _srcList.insert(index, element);
  +  void insert(int index, element) => _srcList.insert(index, element);
   
     void insertAll(int index, Iterable iterable) => _srcList.insertAll(index, iterable);
   
  
positive.code: /**
   * filter follow up rows base on '_parent' and '_collapsed' and id field to render tree view
   */
  class HierarchFilterList extends  FilteredList{
    List<testShowItemFun> filterFun = [];
    String _parentField;
    String _idField;
    String _collapsedField;
    HierarchFilterList._([List items]): super(items){}
  
    /**
     * [parentField] field that describe parent row id, default is '_parent'
  
negative.code:   void add(T value) => innerList.add(value);
  
    void addAll(Iterable<T> all) => innerList.addAll(all);
    void sort([int compare(a, b)]) => innerList.sort(compare);
  }
  
  // code hint for setup grid
  