@Override
    public RecordWriter<NullWritable, VertexWritable> getRecordWriter(final TaskAttemptContext job) throws IOException, InterruptedException {
        return new GryoRecordWriter(getDataOutputStream(job), job.getConfiguration());
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
hadoop-gremlin/src/main/java/org/apache/tinkerpop/gremlin/hadoop/structure/io/gryo/GryoOutputFormat.java