code: func (nodeStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object) {
  	newNode := obj.(*api.Node)
  	oldNode := old.(*api.Node)
  	newNode.Status = oldNode.Status
  
  	if !utilfeature.DefaultFeatureGate.Enabled(features.DynamicKubeletConfig) && !nodeConfigSourceInUse(oldNode) {
  		newNode.Spec.ConfigSource = nil
  	}
  }
docs: // PrepareForUpdate clears fields that are not allowed to be set by end users on update.