When purging content by locationId, purgeByRequest() would receive a Request object with X-Location-Id or X-Group-Location-Id headers indicating which locations to purge.
Inheritance: extends eZ\Publish\Core\MVC\Symfony\Cache\Http\RequestAwarePurger
 /**
  * Purges all content elements currently in cache.
  */
 public function purgeAll()
 {
     $this->cacheStore->purgeAllContent();
 }