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

@param $strippedBlockedItems
@param null $blockingType
@return string