code: func validateKubeConfig(config *clientcmdapi.Config) error {
  	if len(config.Clusters) < 1 {
  		return errors.New("the provided cluster-info kubeconfig file must have at least one Cluster defined")
  	}
  	defaultCluster := kubeconfigutil.GetClusterFromKubeConfig(config)
  	if defaultCluster == nil {
  		return errors.New("the provided cluster-info kubeconfig file must have an unnamed Cluster or a CurrentContext that specifies a non-nil Cluster")
  	}
  	return clientcmd.Validate(*config)
  }
docs: // validateKubeConfig makes sure the user-provided kubeconfig file is valid