code: public function aroundSetHeader(Http $subject, callable $proceed, ...$args) // @codingStandardsIgnoreLine - unused parameter
      {
          // Is Fastly cache enabled?
          if ($this->config->getType() !== Config::FASTLY) {
              return $proceed(...$args);
          }
  
          // Is current header X-Magento-Tags
          if (isset($args[0]) == true && $args[0] !== 'X-Magento-Tags') {
              return $proceed(...$args);
          }
  
          // Make the necessary adjustment
          $args[1] = $this->cacheTags->convertCacheTags(str_replace(',', ' ', $args[1]));
          $tagsSize = $this->config->getXMagentoTagsSize();
          if (strlen($args[1]) > $tagsSize) {
              $trimmedArgs = substr($args[1], 0, $tagsSize);
              $args[1] = substr($trimmedArgs, 0, strrpos($trimmedArgs, ' ', -1));
          }
  
          // Proceed
          return $proceed(...$args);
      }
docs: Alter the X-Magento-Tags header
  
  @param Http $subject
  @param callable $proceed
  @param array ...$args
  @return mixed