code: public function processBlockedItems($strippedBlockedItems, $blockingType = null)
      {
          if (empty($blockingType)) {
              $blockingType = $this->_scopeConfig->getValue(self::XML_FASTLY_BLOCKING_TYPE);
          }
          if ($blockingType == '1') {
              $strippedBlockedItems = '!(' . $strippedBlockedItems . ')';
          }
          return $strippedBlockedItems;
      }
docs: Process blocked items depending on blocking type
  
  @param $strippedBlockedItems
  @param null $blockingType
  @return string