func All(vs []string, f func(string) bool) bool {
	for _, v := range vs {
		if !f(v) {
			return false
		}
	}
	return true
}
All returns `true` if every strings in the slice
satisfy the predicate `f`.
package utils
func Index(vs []string, t string) int {
	for i, v := range vs {
		if v == t {
			return i
		}
	}
	return -1
}
func Include(vs []string, t string) bool {
	return Index(vs, t) >= 0
}
func Any(vs []string, f func(string) bool) bool {
	for _, v := range vs {
		if f(v) {
			return true
		}
	}
	return false
}