public static <T extends Comparable<? super T>> Collector<T, ?, Optional<Long>> rank(T value) {
        return rankBy(value, t -> t, naturalOrder());
    }
Get a {@link Collector} that calculates the <code>RANK()</code> function given natural ordering.
jOOL-java-8/src/main/java/org/jooq/lambda/Agg.java