docs: @Override
    public Streamlet<R> repartition(int numPartitions,
                             SerializableBiFunction<R, Integer, List<Integer>> partitionFn) {
      checkNotNull(partitionFn, "partitionFn cannot be null");
  
      RemapStreamlet<R> retval = new RemapStreamlet<>(this, partitionFn);
      retval.setNumPartitions(numPartitions);
      addChild(retval);
      return retval;
    }