func IsObjectIdHex(s string) bool {
	if len(s) != 24 {
		return false
	}
	_, err := hex.DecodeString(s)
	return err == nil
}
func IsObjectIdHex(s string) bool {
	if len(s) != 24 {
		return false
	}
	_, err := hex.DecodeString(s)
	return err == nil
}
// IsObjectIdHex returns whether s is a valid hex representation of
// an ObjectId. See the ObjectIdHex function.