code: func (n *Mounter) GetFSGroup(pathname string) (int64, error) {
  	hostPath, err := n.ne.EvalSymlinks(pathname, true /* mustExist */)
  	if err != nil {
  		return -1, err
  	}
  	kubeletpath := n.ne.KubeletPath(hostPath)
  	return mount.GetFSGroupLinux(kubeletpath)
  }
docs: // GetFSGroup returns FSGroup of pathname.