code: func (pool *stringPool) ReadAt(index TokenID) (string, error) {
  	if index < TokenID(0) || index >= TokenID(len(pool.items)) {
  		return "", errors.New("index out of range")
  	}
  	pool.RLock()
  	item := pool.items[int(index)]
  	pool.RUnlock()
  	compressed := pool.buffer.Bytes()[item.begin:item.end]
  	decompressed, error := smaz.Decompress(compressed)
  	if error != nil {
  		return "", error
  	}
  	return string(decompressed), nil
  }
docs: // ReadAt converts token ID back to string.