final Document document) {
        // canonical
        final String canonicalUrl = getCanonicalUrl(responseData, document);
        if (canonicalUrl != null && !canonicalUrl.equalsIgnoreCase(responseData.getUrl()) && isValidUrl(canonicalUrl)
                && isValidCanonicalUrl(responseData.getUrl(), canonicalUrl)) {
            final Set<RequestData> childUrlSet = new HashSet<>();