private Optional<ValidationEvent> validateBuiltIn(
            ServiceShape serviceShape,
            String builtInName,
            FromSourceLocation source
    ) {
        if (ADDITIONAL_CONSIDERATION_BUILT_INS.contains(builtInName)) {
            return Optional.of(danger(
                    serviceShape,
                    source,
                    String.format(ADDITIONAL_CONSIDERATION_MESSAGE, builtInName),
                    builtInName));
        }
        return Optional.empty();
    }
Validator that AWS built-ins used in RuleSet parameters are supported.
smithy-aws-endpoints/src/main/java/software/amazon/smithy/rulesengine/aws/validators/RuleSetAwsBuiltInValidator.java