public Stream<R> visitEndpoint(Endpoint endpoint) {
        return Stream.concat(
                endpoint.getUrl().accept(this),
                endpoint.getProperties().values().stream().flatMap(value -> value.accept(this)));
    }
{@link Endpoint} visitor method.

@param endpoint the endpoint to visit.
@return a stream of values.
smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/language/TraversingVisitor.java