anchor.diff:      _shouldIndent = true;
     }
   
  -  void write(String str) {
  +  void write(str) {
       if (_shouldIndent) {
         _shouldIndent = false;
         _content += _indent;
       }
  -    _content += str;
  +    _content += str.toString();
     }
   
     String toString() => _content;
  
positive.code:       writer.indent();
  
        if (g.node(w) is Map) {
          g.node(w).forEach((val, key) {
            writer.writeLine("${id(key)}=${id(val)};");
          });
        }
  
negative.code: 
    var graphAttrs = g.graph();
    if (graphAttrs is Map) {
      graphAttrs.forEach((k, v) {
        writer.writeLine("${id(k)}=${id(v)};");
      });
    }
  