docs: public static List<Writable> getUniqueSequence(String columnName, Schema schema,
                      JavaRDD<List<List<Writable>>> sequenceData) {
          JavaRDD<List<Writable>> flattenedSequence = sequenceData.flatMap(new SequenceFlatMapFunction());
          return getUnique(columnName, schema, flattenedSequence);
      }