@Override
    public <V> BinaryOperator<V> getReducer(final String key) {
        return this.sideEffects.getReducer(key);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/traversal/MemoryTraversalSideEffects.java