private Stream<? extends Shape> streamStartingShapes(Collection<? extends Shape> startingShapes) {
        return isParallel(startingShapes) ? startingShapes.parallelStream() : startingShapes.stream();
    }
Uses parallel streams when the model size exceeds this number.
smithy-model/src/main/java/software/amazon/smithy/model/selector/WrappedSelector.java