code: func RunListTokens(out io.Writer, errW io.Writer, client clientset.Interface) error {
  	// First, build our selector for bootstrap tokens only
  	klog.V(1).Infoln("[token] preparing selector for bootstrap token")
  	tokenSelector := fields.SelectorFromSet(
  		map[string]string{
  			// TODO: We hard-code "type" here until `field_constants.go` that is
  			// currently in `pkg/apis/core/` exists in the external API, i.e.
  			// k8s.io/api/v1. Should be v1.SecretTypeField
  			"type": string(bootstrapapi.SecretTypeBootstrapToken),
  		},
  	)
  	listOptions := metav1.ListOptions{
  		FieldSelector: tokenSelector.String(),
  	}
  
  	klog.V(1).Infoln("[token] retrieving list of bootstrap tokens")
  	secrets, err := client.CoreV1().Secrets(metav1.NamespaceSystem).List(listOptions)
  	if err != nil {
  		return errors.Wrap(err, "failed to list bootstrap tokens")
  	}
  
  	w := tabwriter.NewWriter(out, 10, 4, 3, ' ', 0)
  	fmt.Fprintln(w, "TOKEN\tTTL\tEXPIRES\tUSAGES\tDESCRIPTION\tEXTRA GROUPS")
  	for _, secret := range secrets.Items {
  
  		// Get the BootstrapToken struct representation from the Secret object
  		token, err := kubeadmapi.BootstrapTokenFromSecret(&secret)
  		if err != nil {
  			fmt.Fprintf(errW, "%v", err)
  			continue
  		}
  
  		// Get the human-friendly string representation for the token
  		humanFriendlyTokenOutput := humanReadableBootstrapToken(token)
  		fmt.Fprintln(w, humanFriendlyTokenOutput)
  	}
  	w.Flush()
  	return nil
  }
docs: // RunListTokens lists details on all existing bootstrap tokens on the server.