public static JavaPairRDD<Object, VertexWritable> loadVertices(
        final org.apache.commons.configuration2.Configuration sparkGraphConfiguration,
        final JavaSparkContext sparkContext) {
        assert sparkGraphConfiguration.containsKey(Constants.GREMLIN_HADOOP_GRAPH_READER);
        logger.debug("Loading vertices into Spark RDD...");
        final Configuration hadoopConfiguration = ConfUtil.makeHadoopConfiguration(sparkGraphConfiguration);
        return loadVertices(createInputRDD(hadoopConfiguration), sparkGraphConfiguration, sparkContext);
    }
Load graph into Spark RDDs. Note: Graph configurations must include {@value Constants#GREMLIN_HADOOP_GRAPH_READER}.
<p>
See Example below:
<pre>
    SparkConf sparkConf = new SparkConf().setAppName("Spark Graph")
        .set(SparkLauncher.SPARK_MASTER, "local[4]")
        .set(Constants.SPARK_SERIALIZER, GryoSerializer.class.getCanonicalName());
    JavaSparkContext sparkContext = new JavaSparkContext(sparkConf);

    Configuration sparkGraphConfiguration = new BaseConfiguration();
    sparkGraphConfiguration.setProperty(Constants.GREMLIN_HADOOP_GRAPH_READER, GryoInputFormat.class.getCanonicalName());
    sparkGraphConfiguration.setProperty(Constants.MAPREDUCE_INPUT_FILEINPUTFORMAT_INPUTDIR,
        SparkHadoopGraphProvider.PATHS.get("tinkerpop-modern-v3.kryo"));

    // load vertices
    JavaPairRDD verticesRDD = SparkIOUtil.loadVertices(sparkGraphConfiguration, sparkContext);
</pre>

@param sparkGraphConfiguration graph configurations
@param sparkContext            a JavaSparkContext instance
@return vertices in Spark RDD
spark-gremlin/src/main/java/org/apache/tinkerpop/gremlin/spark/structure/io/SparkIOUtil.java