code: func (c *Cloud) ExternalID(nodeName types.NodeName) (string, error) {
  	if c.selfAWSInstance.nodeName == nodeName {
  		// We assume that if this is run on the instance itself, the instance exists and is alive
  		return c.selfAWSInstance.awsID, nil
  	}
  	// We must verify that the instance still exists
  	// Note that if the instance does not exist or is no longer running, we must return ("", cloudprovider.InstanceNotFound)
  	instance, err := c.findInstanceByNodeName(nodeName)
  	if err != nil {
  		return "", err
  	}
  	if instance == nil {
  		return "", cloudprovider.ErrInstanceNotFound
  	}
  	return orEmpty(instance.InstanceId), nil
  }
docs: // ExternalID returns the cloud provider ID of the node with the specified nodeName (deprecated).