public SparkGraphComputer graphStorageLevel(final StorageLevel storageLevel) {
        return configure(GREMLIN_SPARK_GRAPH_STORAGE_LEVEL, storageLevel.description());
    }
Specifies the method by which the {@link VertexProgram} created graph is persisted. By default, it is configured
to use {@code StorageLevel#MEMORY_ONLY()}
spark-gremlin/src/main/java/org/apache/tinkerpop/gremlin/spark/process/computer/SparkGraphComputer.java