public default <K, V> JavaPairRDD<K, V> readMemoryRDD(final Configuration configuration, final String memoryKey, final JavaSparkContext sparkContext) {
        return sparkContext.<Tuple2<K, V>>emptyRDD().mapToPair(t -> t);
    }
Read a memoryRDD from the storage location.
The default implementation returns an empty RDD.

@param configuration the configuration for the {@link SparkGraphComputer}
@param memoryKey     the memory key of the memoryRDD
@param sparkContext  the Spark context with the requisite methods for generating a {@link JavaPairRDD}
@param <K>           the key class of the memoryRDD
@param <V>           the value class of the memoryRDD
@return the memoryRDD with respective key/value pairs.
spark-gremlin/src/main/java/org/apache/tinkerpop/gremlin/spark/structure/io/InputRDD.java