*<Null safety>*
Iterable<T> expand <T>(Iterable<T> f(E)) inherited
var input = [1, 2, 3]; var duplicated = input.expand((i) => [i, i]).toList(); print(duplicated); // => [1, 1, 2, 2, 3, 3]
@override Iterable<T> expand<T>(Iterable<T> Function(E) f) => _base.expand(f);