private function mergeSelf(UncachersPool $uncacher)
 {
     foreach ($uncacher->getUncachers() as $subUncacher) {
         $this->merge($subUncacher);
     }
     return $this;
 }
 private function triggerUncacher()
 {
     if ($this->uncacher) {
         $this->uncacher->uncache();
         $this->uncacher = null;
     }
 }