groupBy<S, T> function
*<Null safety>*
Map<T, List<S>> groupBy <S, T>(Iterable<S> values, T key(S))
Implementation
Map<T, List<S>> groupBy<S, T>(Iterable<S> values, T Function(S) key) {
var map = <T, List<S>>{};
for (var element in values) {
(map[key(element)] ??= []).add(element);
}
return map;
}