@Nonnull
    public Type require(String id) {
        nonNull(id, "id");
        return usedTypes.computeIfAbsent(id, i -> {
            Type type = types.get(id);
            if (type == null) {
                // Copy data as the ArtifactHandler is not immutable, but Type should be.
                ArtifactHandler handler = manager.getArtifactHandler(id);
                type = new DefaultType(
                        id,