concatAll method
Concatenates this iterable and a provided iterable of iterables.
Flattens the elements in iterables
into a single iterable and then
appends the elements of that iterable to the end of this iterable.
Implementation
Iterable<T> concatAll(Iterable<Iterable<T>> iterables) sync* {
yield* this;
for (var iterable in iterables) {
yield* iterable;
}
}