code: func (s *LDBStore) MarkAccessed(addr Address) {
  	s.lock.Lock()
  	defer s.lock.Unlock()
  
  	if s.closed {
  		return
  	}
  
  	proximity := s.po(addr)
  	s.tryAccessIdx(addr, proximity)
  }
docs: // MarkAccessed increments the access counter as a best effort for a chunk, so
  // the chunk won't get garbage collected.