default List<SortableFeature> toList() {
    List<SortableFeature> list = new ArrayList<>();
    for (SortableFeature entry : this) {
      list.add(entry);
    }
    return list;
  }
Returns all elements in a list. WARNING: this will materialize all elements in-memory.
planetiler-core/src/main/java/com/onthegomap/planetiler/collection/FeatureSort.java