// hand side of a comparison. This is useful in testing to assert that an
// object is a derivative.
func IgnoreUnset() cmp.Option {
	return cmp.Options{
		// ignore unset fields in v2
		cmp.FilterPath(func(path cmp.Path) bool {
			_, v2 := path.Last().Values()
			switch v2.Kind() {
			case reflect.Slice, reflect.Map:
				if v2.IsNil() || v2.Len() == 0 {
					return true
				}
			case reflect.String: