private List<Set<Shape>> computeRoots(Model model) {
        NeighborProviderIndex index = NeighborProviderIndex.of(model);
        List<Set<Shape>> rootResults = new ArrayList<>(roots.size());
        for (InternalSelector selector : roots) {
            Set<Shape> result = evalRoot(model, index, selector, rootResults);
            rootResults.add(result);
        }
        return rootResults;
    }
Uses parallel streams when the model size exceeds this number.
smithy-model/src/main/java/software/amazon/smithy/model/selector/WrappedSelector.java