docs: def inline_transform(filename, key):
      """Encrypt file inline.
  
      Encrypts a given file with the given key,
      and replaces it directly without any extra
      space requirement.
  
      :param filename: The name of the file to encrypt.
      :type filename: str
      :param key: The key used to encrypt the file.
      :type key: str
      """
      pos = 0
      for chunk, fp in iter_transform(filename, key):
          fp.seek(pos)
          fp.write(chunk)
          fp.flush()
          pos = fp.tell()