public static <S> S reduce(final Iterable<S> iterable, final S identity, final BinaryOperator<S> accumulator) {
        return reduce(iterable.iterator(), identity, accumulator);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/util/iterator/IteratorUtils.java