code: func (g *Cloud) instanceByProviderID(providerID string) (*gceInstance, error) {
  	project, zone, name, err := splitProviderID(providerID)
  	if err != nil {
  		return nil, err
  	}
  
  	instance, err := g.getInstanceFromProjectInZoneByName(project, zone, name)
  	if err != nil {
  		if isHTTPErrorCode(err, http.StatusNotFound) {
  			return nil, cloudprovider.InstanceNotFound
  		}
  		return nil, err
  	}
  
  	return instance, nil
  }
docs: // instanceByProviderID returns the cloudprovider instance of the node
  // with the specified unique providerID