code: func (mounter *Mounter) IsLikelyNotMountPoint(file string) (bool, error) {
  	stat, err := os.Stat(file)
  	if err != nil {
  		return true, err
  	}
  	rootStat, err := os.Lstat(filepath.Dir(strings.TrimSuffix(file, "/")))
  	if err != nil {
  		return true, err
  	}
  	// If the directory has a different device as parent, then it is a mountpoint.
  	if stat.Sys().(*syscall.Stat_t).Dev != rootStat.Sys().(*syscall.Stat_t).Dev {
  		return false, nil
  	}
  
  	return true, nil
  }
docs: // IsLikelyNotMountPoint determines if a directory is not a mountpoint.
  // It is fast but not necessarily ALWAYS correct. If the path is in fact
  // a bind mount from one part of a mount to another it will not be detected.
  // mkdir /tmp/a /tmp/b; mount --bind /tmp/a /tmp/b; IsLikelyNotMountPoint("/tmp/b")
  // will return true. When in fact /tmp/b is a mount point. If this situation
  // if of interest to you, don't use this function...