anchor.diff:      x._level = level;
       x._root = root;
       x._tail = tail;
  -    x.__ownerID = ownerID;
  +    x._owner = ownerID;
       return x;
     }
   
  
positive.code: 
    BaseVectorImpl._prototype() {
      this._origin = 0;
      this.__ownerID = null;
      this._root = new _VNode([], __ownerID);
      this._tail = _root;
      this._level = _SHIFT;
      this._size = 0;
  
negative.code:     x._level = level;
      x._root = root;
      x._tail = tail;
      x._owner = null;
      return x;
    }
  
  