code: public function afterSave(\Magento\Config\Model\Config $subject) // @codingStandardsIgnoreLine - unused parameter
      {
          if ($this->purge) {
              $this->api->cleanBySurrogateKey(['text']);
          }
      }
docs: Trigger purge if set
  
  @param \Magento\Config\Model\Config $subject
  @throws \Zend_Uri_Exception