protected Optional<BiFunction<TransformContext, T, List<String>>> getAdditionalProjectionsFunction() {
        return Optional.empty();
    }
@return an Optional of either a BiFunction that returns the additional
        projections to run after this one, or empty to indicate this
        projection will never compose other ones.
smithy-build/src/main/java/software/amazon/smithy/build/transforms/ConfigurableProjectionTransformer.java