func TestKeys() {
	want := []int{1, 2, 4, 8}

	got1 := _Keys(m1)
	sort.Ints(got1)
	if !_SliceEqual(got1, want) {
		panic(fmt.Sprintf("_Keys(%v) = %v, want %v", m1, got1, want))
	}

	got2 := _Keys(m2)
	sort.Ints(got2)
	if !_SliceEqual(got2, want) {
		panic(fmt.Sprintf("_Keys(%v) = %v, want %v", m2, got2, want))
	}
}

func TestValues() {
	got1 := _Values(m1)

		if v1 != v2 {
			isNaN := func(f Elem) bool { return f != f }
			if !isNaN(v1) || !isNaN(v2) {
				return false
			}
		}
	}
	return true
}

// _Keys returns the keys of the map m.
// The keys will be an indeterminate order.
func _Keys[K comparable, V any](m map[K]V) []K {
	r := make([]K, 0, len(m))
	for k := range m {
		r = append(r, k)
	}
	return r