code: func waitForTLSBootstrappedClient() error {
  	fmt.Println("[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...")
  
  	// Loop on every falsy return. Return with an error if raised. Exit successfully if true is returned.
  	return wait.PollImmediate(kubeadmconstants.APICallRetryInterval, kubeadmconstants.TLSBootstrapTimeout, func() (bool, error) {
  		// Check that we can create a client set out of the kubelet kubeconfig. This ensures not
  		// only that the kubeconfig file exists, but that other files required by it also exist (like
  		// client certificate and key)
  		_, err := kubeconfigutil.ClientSetFromFile(kubeadmconstants.GetKubeletKubeConfigPath())
  		return (err == nil), nil
  	})
  }
docs: // waitForTLSBootstrappedClient waits for the /etc/kubernetes/kubelet.conf file to be available