It Invert

entries := func(yield func(string, int) bool) {
    _ = yield("apple", 1)
    _ = yield("banana", 2)
    _ = yield("cherry", 3)
}
inverted := it.Invert(entries)
var keys []int
var values []string
for k, v := range inverted {
    keys = append(keys, k)
    values = append(values, v)
}
// keys contains 1, 2, 3 and values contains "apple", "banana", "cherry"