@Override
    public final StringProperty stringPropertyOf(String key, Supplier<String> ifEmpty) {
        return (StringProperty) properties.computeIfAbsent(key, k -> prepare(k, new SimpleStringProperty(), ifEmpty.get()));
    }
{@inheritDoc}
@deprecated Not supported for observables
tool-parent/tool-config/src/main/java/com/speedment/tool/config/AbstractDocumentProperty.java