addAll method Null safety
override
Adds all elements
to this set.
Equivalent to adding each element in elements
using add,
but some collections may be able to optimize it.
final characters = <String>{'A', 'B'};
characters.addAll({'A', 'B', 'C'});
print(characters); // {A, B, C}
Implementation
@override
void addAll(Iterable<String?> elements) => _inner.addAll(elements);