docs: def parsePermission3Char(permission):
      """
      'rwx' 形式のアクセス権限文字列 permission を8進数形式に変換する
  
      :return:
      :rtype: int
      """
  
      if len(permission) != 3:
          raise ValueError(permission)
  
      permission_int = 0
      if permission[0] == "r":
          permission_int += 4
      if permission[1] == "w":
          permission_int += 2
      if permission[2] == "x":
          permission_int += 1
  
      return permission_int