@Override
    public final OptionalLong getAsLong(String key) {
        final LongProperty prop = (LongProperty) properties.get(key);
        if (prop == null) {
            return OptionalLong.empty();
        } else {
            return OptionalUtil.ofNullable(prop.getValue());
        }
    }
{@inheritDoc}
@deprecated Not supported for observables
tool-parent/tool-config/src/main/java/com/speedment/tool/config/AbstractDocumentProperty.java