code: func (u *FakeVolumeUtil) IsBlock(fullPath string) (bool, error) {
  	dir, file := filepath.Split(fullPath)
  	dir = filepath.Clean(dir)
  	files, found := u.directoryFiles[dir]
  	if !found {
  		return false, fmt.Errorf("Directory %q not found", dir)
  	}
  
  	for _, f := range files {
  		if file == f.Name {
  			return f.VolumeType == FakeEntryBlock, nil
  		}
  	}
  	return false, fmt.Errorf("Directory entry %q not found", fullPath)
  }
docs: // IsBlock checks if the given path is a block device