public static void registerInputOutputPair(final Class<? extends InputFormat<NullWritable, VertexWritable>> inputFormat, final Class<? extends OutputFormat<NullWritable, VertexWritable>> outputFormat) {
        INPUT_TO_OUTPUT_CACHE.put(inputFormat, outputFormat);
        OUTPUT_TO_INPUT_CACHE.put(outputFormat, inputFormat);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
hadoop-gremlin/src/main/java/org/apache/tinkerpop/gremlin/hadoop/structure/io/InputOutputHelper.java