public SortableChunk sort() {
        if (parallelSort) {
          Arrays.parallelSort(featuresToSort);
        } else {
          Arrays.sort(featuresToSort);
        }
        return this;
      }
A container for all features in a chunk read into memory for sorting.
planetiler-core/src/main/java/com/onthegomap/planetiler/collection/ExternalMergeSort.java