code: func (g Glob) Validate() error {
  	chunks := strings.SplitN(string(g), ":", 2)
  	if len(chunks) != 2 {
  		return fmt.Errorf("auth: bad identity glob string %q", g)
  	}
  	if knownKinds[Kind(chunks[0])] == nil {
  		return fmt.Errorf("auth: bad identity glob kind %q", chunks[0])
  	}
  	if chunks[1] == "" {
  		return fmt.Errorf("auth: identity glob can't be empty")
  	}
  	if _, err := cache.translate(chunks[1]); err != nil {
  		return fmt.Errorf("auth: bad identity glob pattern %q - %s", chunks[1], err)
  	}
  	return nil
  }
docs: // Validate checks that the identity glob string is well-formed.