anchor.diff:  part of domnode;
  +// TODO: remove validator y sanitizer from constructors
  +// TODO: simplify the '$' function
  +// TODO: add a 'query' function
   
   /**
    * This class represents one or more DOM elements.
  
positive.code:       throw new ArgumentError(new ParserError(result).toString());
      }
  
      DomParser domParser = new DomParser();
      Document doc = domParser.parseFromString(str, type);
      _elements = [doc.documentElement];
    }
  
    List<Element> get elements => this._elements;
  
negative.code:     _elements = elements;
    }
  
    // TODO: we do not need 'type' (or replace it by isXml)
    DomNode.fromString(String str,
        {String type: 'text/xml',
        NodeValidator validator,
  