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<>();

     *     exception by calling [HttpUrl.parse]; it returns null for invalid URLs.
     */
    open fun url(url: String): Builder = url(canonicalUrl(url).toHttpUrl())

    // Silently replace web socket URLs with HTTP URLs.
    private fun canonicalUrl(url: String) =
      when {
        url.startsWith("ws:", ignoreCase = true) -> "http:${url.substring(3)}"

	// Get canonical URI.
	canonicalURI := s3utils.EncodePath(req.URL.Path)

	// Get canonical request.
	// canonicalRequest =
	//  <HTTPMethod>\n
	//  <CanonicalURI>\n
	//  <CanonicalQueryString>\n
	//  <CanonicalHeaders>\n
	//  <SignedHeaders>\n
	//  <HashedPayload>
	//
	canonicalRequest := strings.Join([]string{
		req.Method,
		canonicalURI,
		req.URL.RawQuery,
		canonicalHeaders,