code: public CloseableIterator<T> mergeSortedChunks(List<File> sortedChunks) throws IOException {
          return mergeSortedChunksNoPartialMerge(partialMerge(sortedChunks));
      }
docs: Returns an iterator over the sorted result. Takes a list of already sorted chunk files as
  input. Note that this method is normally used with one of the writeSortedChunks methods.
  @param sortedChunks a list of sorted chunk files
  @return an iterator the iterates over the sorted result.
  @throws IOException if something fails when doing I/O.