public static HadoopGraph open(final Configuration configuration) {
        return new HadoopGraph(Optional.ofNullable(configuration).orElse(EMPTY_CONFIGURATION));
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
hadoop-gremlin/src/main/java/org/apache/tinkerpop/gremlin/hadoop/structure/HadoopGraph.java