anchor.diff:  
     return res;
   }
  -
  -
  -
  -
  -/// WRONG
  -dynamic _flattenLevel2(dynamic x, int level, {List<String> levelNames}) {
  -  List<Map> res = [];
  -  /// keep flattening
  -  if (levelNames.isEmpty || levelNames.length < level+1) {
  -    levelNames.add('level$level');
  -  }
  -  if (x is Map) {
  -    x.keys.forEach((k) {
  -      print('level: $level, name: ${levelNames[level]}, key: $k');
  -      print('x[k]: ${x[k]}');
  -      Map aux = _flattenLevel(x[k], level+1, levelNames: levelNames);
  -      res.add({levelNames[level]: k}..addAll(aux));
  -    });
  -  } else {
  -    res.add({levelNames[level]: x});
  -  }
  -
  -  return res;
  -}
  -
  -
  -
  
positive.code: ///
  List<Map> flattenMap(Map m, {List<String> levelNames}) {
    levelNames ??= [];
    return _flattenLevel(m, 0, levelNames: levelNames);
  }
  
  
  
  
  dynamic _flattenLevel(Map x, {List<String> levelNames}) {
    List<Map> res = [];
    int level = 0;
  
    x.keys.forEach((k) {
      if (levelNames.isEmpty || levelNames.length < level+1) {
        levelNames.add('level$level');
      }
      Map row = {levelNames[level]: x[k]};
  
  
  
    });
  
  
    /// keep flattening
    if (x is Map) {
      x.keys.forEach((k) {
        print('level: $level, name: ${levelNames[level]}, key: $k');
        print('x[k]: ${x[k]}');
        Map aux = _flattenLevel(x[k], level+1, levelNames: levelNames);
        res.add({levelNames[level]: k}..addAll(aux));
      });
    } else {
  
negative.code: library nest;
  
  /// Take a nested map [m] and return a one-level new map.
  /// For example given the input map:
  