default StringProperty enumConstantsProperty() {
        return stringPropertyOf(HasEnumConstantsUtil.ENUM_CONSTANTS,
            () -> HasEnumConstants.super.getEnumConstants().orElse(null)
        );
    }
Observable property for the {@link #getEnumConstants()}-fields. The value
may be {@code null}.

@return  the observable property for enum constants
tool-parent/tool-config/src/main/java/com/speedment/tool/config/trait/HasEnumConstantsProperty.java