@Override
    public Model transform(TransformContext context) {
        Model model = context.getModel();
        return context.getTransformer().makeIdempotencyTokensClientOptional(model);
    }
{@code makeIdempotencyTokensClientOptional} makes {@code @idempotencyToken} fields {@code @clientOptional}.
smithy-build/src/main/java/software/amazon/smithy/build/transforms/MakeIdempotencyTokensClientOptional.java