code: func ensureNodeExistsByProviderID(instances cloudprovider.Instances, node *v1.Node) (bool, error) {
  	providerID := node.Spec.ProviderID
  	if providerID == "" {
  		var err error
  		providerID, err = instances.InstanceID(context.TODO(), types.NodeName(node.Name))
  		if err != nil {
  			if err == cloudprovider.InstanceNotFound {
  				return false, nil
  			}
  			return false, err
  		}
  
  		if providerID == "" {
  			klog.Warningf("Cannot find valid providerID for node name %q, assuming non existence", node.Name)
  			return false, nil
  		}
  	}
  
  	return instances.InstanceExistsByProviderID(context.TODO(), providerID)
  }
docs: // ensureNodeExistsByProviderID checks if the instance exists by the provider id,
  // If provider id in spec is empty it calls instanceId with node name to get provider id