code: def load(cls, directory):
      
      read_file = maybe_read_file(cls._path(directory))
      if read_file:
        fingerprint, length = read_file.split(':')
        return Digest(fingerprint, int(length))
      else:
        return None
docs: Load a Digest from a `.digest` file adjacent to the given directory.
  
      :return: A Digest, or None if the Digest did not exist.