code: func certificateAuthorityFormat(bytes []byte) (string, error) {
  	_, _, _, _, err := ssh.ParseAuthorizedKey(bytes)
  	if err != nil {
  		_, _, _, _, _, err := ssh.ParseKnownHosts(bytes)
  		if err != nil {
  			return "", trace.BadParameter("unknown ca format")
  		}
  		return teleport.KnownHosts, nil
  	}
  	return teleport.AuthorizedKeys, nil
  }
docs: // certificateAuthorityFormat parses bytes and determines if they are in
  // known_hosts format or authorized_keys format.