Method is

src/main/java/org/jsoup/select/QueryParser.java:432–434

()

    // pseudo selector :is()
    private Evaluator is() {
        return parseNested(StructuralEvaluator.Is::new, ":is() must have a selector");
    }

    private Evaluator parseNested(Function<Evaluator, Evaluator> func, String err) {
        Validate.isTrue(tq.matchChomp('('), err);