@Override
    public void merge(final AccumulatorV2<ObjectWritable<A>, ObjectWritable<A>> other) {
        this.add(other.value());
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
@author Stephen Mallette (http://stephen.genoprime.com)
spark-gremlin/src/main/java/org/apache/tinkerpop/gremlin/spark/process/computer/MemoryAccumulator.java