code: func doCleanSubPath(mounter mount.Interface, fullContainerDirPath, subPathIndex string) error {
  	// process /var/lib/kubelet/pods/<uid>/volume-subpaths/<volume>/<container name>/<subPathName>
  	klog.V(4).Infof("Cleaning up subpath mounts for subpath %v", subPathIndex)
  	fullSubPath := filepath.Join(fullContainerDirPath, subPathIndex)
  
  	if err := mount.CleanupMountPoint(fullSubPath, mounter, true); err != nil {
  		return fmt.Errorf("error cleaning subpath mount %s: %s", fullSubPath, err)
  	}
  
  	klog.V(4).Infof("Successfully cleaned subpath directory %s", fullSubPath)
  	return nil
  }
docs: // doCleanSubPath tears down the single subpath bind mount