@Override
    public <V> void register(final String key, final Supplier<V> initialValue, final BinaryOperator<V> reducer) {

    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/util/EmptyTraversalSideEffects.java