code: public function aroundSendPurgeRequest(PurgeCache $subject, callable $proceed, ...$args) // @codingStandardsIgnoreLine - unused parameter
      {
          if ($this->config->isFastlyEnabled() !== true) {
              $proceed(...$args);
          }
      }
docs: Prevent Magento from executing purge requests on Varnish when Fastly is enabled
  
  @param PurgeCache $subject
  @param callable $proceed
  @param array ...$args