private String detectWriter() {
        if (file.endsWith(".kryo"))
            return GryoOutputFormat.class.getName();
        else if (file.endsWith(".json"))
            return GraphSONOutputFormat.class.getName();
        else if (file.endsWith(".xml"))
            throw new IllegalStateException("GraphML is not a supported file format for OLAP");
        else
            throw new IllegalStateException("Could not detect the file format - specify the reader explicitly or rename file with a standard extension");
    }
Overwrites all configurations from values passed using {@link GraphTraversal#with(String, Object)}.
hadoop-gremlin/src/main/java/org/apache/tinkerpop/gremlin/hadoop/process/computer/traversal/step/sideEffect/HadoopIoStep.java