code: func toBoolean(value string) (interface{}, error) {
  	switch strings.ToLower(value) {
  	case "y", "yes", "true", "on":
  		return true, nil
  	case "n", "no", "false", "off":
  		return false, nil
  	default:
  		return nil, errors.Errorf("invalid boolean: %s", value)
  	}
  }
docs: // should match http://yaml.org/type/bool.html