code: func (ttles *TTLExpirationScheduler) AddManifest(manifestRef reference.Canonical, ttl time.Duration) error {
  	ttles.Lock()
  	defer ttles.Unlock()
  
  	if ttles.stopped {
  		return fmt.Errorf("scheduler not started")
  	}
  
  	ttles.add(manifestRef, ttl, entryTypeManifest)
  	return nil
  }
docs: // AddManifest schedules a manifest cleanup after ttl expires