code: func azToRegion(az string) (string, error) {
  	if len(az) < 1 {
  		return "", fmt.Errorf("invalid (empty) AZ")
  	}
  	region := az[:len(az)-1]
  	return region, nil
  }
docs: // Derives the region from a valid az name.
  // Returns an error if the az is known invalid (empty)