    "The type of the value that indicates that an [[Iterator]]
     is exhausted and has no more values to return."
    see (`interface Iterator`)
    tagged("Streams")
    shared abstract class Finished() of finished {}

    "A value that indicates that an [[Iterator]] is exhausted
     and has no more values to return."
    see (`interface Iterator`)
    tagged("Streams")
    shared object finished extends Finished() {
        string => "finished";
    }