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