static boolean isMarkedNullable(AnnotatedElement typeElement) {
        try {
            return IS_MARKED_NULLABLE != null &&
                   (boolean) IS_MARKED_NULLABLE.invoke(null, typeElement);
        } catch (Exception e) {
            return false;
        }
    }
Returns true if the typeElement can be converted to KType and is marked nullable.
core/src/main/java/com/linecorp/armeria/internal/server/annotation/KotlinUtil.java