code: func GetGCERegion(zone string) (string, error) {
  	ix := strings.LastIndex(zone, "-")
  	if ix == -1 {
  		return "", fmt.Errorf("unexpected zone: %s", zone)
  	}
  	return zone[:ix], nil
  }
docs: // GetGCERegion returns region of the gce zone. Zone names
  // are of the form: ${region-name}-${ix}.
  // For example, "us-central1-b" has a region of "us-central1".
  // So we look for the last '-' and trim to just before that.