/**
  * Removes all cache entries of this cache which are tagged by the specified tag.
  *
  * @param string $tag The tag the entries must have
  * @return void
  * @author Robert Lemke <*****@*****.**>
  * @author Karsten Dambekalns <*****@*****.**>
  */
 public function flushByTag($tag)
 {
     if (!$this->isValidTag($tag)) {
         throw new InvalidArgumentException('"' . $tag . '" is not a valid tag for a cache entry.', 1233057359);
     }
     $this->backend->flushByTag($tag);
 }