code: func baseTwoKeys(key []byte) (string, string, error) {
  	parts := bytes.Split(key, []byte{backend.Separator})
  	if len(parts) < 2 {
  		return "", "", trace.NotFound("failed parsing %v", string(key))
  	}
  	return string(parts[len(parts)-2]), string(parts[len(parts)-1]), nil
  }
docs: // baseTwoKeys returns two last keys