It Contains

seq := func(yield func(int) bool) {
    _ = yield(10)
    _ = yield(20)
    _ = yield(30)
}
has := it.Contains(seq, 20)
// has == true

seq := func(yield func(string) bool) {
    _ = yield("apple")
    _ = yield("banana")
    _ = yield("cherry")
}
has := it.Contains(seq, "orange")
// has == false