code: @SuppressWarnings("checkstyle:MissingSwitchDefault")
      private CrawlDelayMechanism createCrawlDelayMechanism() {
          switch (config.getCrawlDelayStrategy()) {
              case FIXED:
                  return new FixedCrawlDelayMechanism(config);
              case RANDOM:
                  return new RandomCrawlDelayMechanism(config);
              case ADAPTIVE:
                  return new AdaptiveCrawlDelayMechanism(config, (JavascriptExecutor) webDriver);
          }
  
          throw new IllegalArgumentException("Unsupported crawl delay strategy.");
      }
docs: Creates the crawl delay mechanism according to the configuration.
  
  @return the created crawl delay mechanism