code: public function cleanAll()
      {
          // Check if purge has been requested on this request
          if ($this->purged == true) {
              return true;
          }
          $this->purged = true;
  
          $type = 'clean/purge all';
          $uri = $this->_getApiServiceUri() . 'purge_all';
          $result = $this->_purge($uri, null);
          if ($result['status']) {
              $this->logger->execute('clean all items');
          }
  
          $canPublishPurgeAllChanges = $this->config->canPublishPurgeAllChanges();
          $canPublishPurgeChanges = $this->config->canPublishPurgeChanges();
  
          if ($this->config->areWebHooksEnabled() && ($canPublishPurgeAllChanges || $canPublishPurgeChanges)) {
              $this->sendWebHook('*initiated clean/purge all*');
  
              $canPublishPurgeAllDebugBacktrace = $this->config->canPublishPurgeAllDebugBacktrace();
              $canPublishPurgeDebugBacktrace = $this->config->canPublishPurgeDebugBacktrace();
  
              if ($canPublishPurgeAllDebugBacktrace == false && $canPublishPurgeDebugBacktrace == false) {
                  return $result['status'];
              }
  
              $this->stackTrace($type);
          }
  
          return $result['status'];
      }
docs: Purge all of Fastly's CDN content. Can be called only once per request
  
  @return bool|\Magento\Framework\Controller\Result\Json
  @throws \Zend_Uri_Exception