groupListsBy<K> method

*<Null safety>*

Map<K, List<T>> groupListsBy <K>(K keyOf(T element))

Implementation

Map<K, List<T>> groupListsBy<K>(K Function(T element) keyOf) {
  var result = <K, List<T>>{};
  for (var element in this) {
    (result[keyOf(element)] ??= [])..add(element);
  }
  return result;
}