code: func printConfiguration(clustercfg *kubeadmapi.ClusterConfiguration, w io.Writer) {
  	// Short-circuit if cfg is nil, so we can safely get the value of the pointer below
  	if clustercfg == nil {
  		return
  	}
  
  	cfgYaml, err := configutil.MarshalKubeadmConfigObject(clustercfg)
  	if err == nil {
  		fmt.Fprintln(w, "[upgrade/config] Configuration used:")
  
  		scanner := bufio.NewScanner(bytes.NewReader(cfgYaml))
  		for scanner.Scan() {
  			fmt.Fprintf(w, "\t%s\n", scanner.Text())
  		}
  	}
  }
docs: // printConfiguration prints the external version of the API to yaml