public Optional<String> toPredefinedName() {
        return PREDEFINED.entrySet().stream()
            .filter(e -> e.getValue().equals(this))
            .map(Map.Entry::getKey)
            .findFirst();
    }
@return the name if this is a predefined capability set, or empty if not
security-utils/src/main/java/com/yahoo/security/tls/CapabilitySet.java