func containsRune(s string, r rune) bool {
	for _, c := range s {
		if c == r {
			return true
		}
	}
	return false
}

// Trim returns a subslice of s by slicing off all leading and
// trailing UTF-8-encoded code points contained in cutset.
func Trim(s []byte, cutset string) []byte {
	if len(s) == 0 {
		// This is what we've historically done.
		return nil
	}
	if cutset == "" {
		return s
	}