code: def chmod_r(root: str, permission: int) -> None:
      
      os.chmod(root, permission)
      for dirpath, dirnames, filenames in os.walk(root):
          for d in dirnames:
              os.chmod(os.path.join(dirpath, d), permission)
          for f in filenames:
              os.chmod(os.path.join(dirpath, f), permission)
docs: Recursive ``chmod``.
  
      Args:
          root: directory to walk down
          permission: e.g. ``e.g. stat.S_IWUSR``