code: func (kubemarkController *KubemarkController) GetNodeGroupForNode(node string) (string, error) {
  	pod := kubemarkController.getPodByName(node)
  	if pod == nil {
  		return "", fmt.Errorf("node %s does not exist", node)
  	}
  	nodeGroup, ok := pod.ObjectMeta.Labels[nodeGroupLabel]
  	if ok {
  		return nodeGroup, nil
  	}
  	return "", fmt.Errorf("can't find nodegroup for node %s due to missing label %s", node, nodeGroupLabel)
  }
docs: // GetNodeGroupForNode returns the name of the node group to which the node
  // belongs.