code: def load_from_file(cls, filename_prefix):
      
      filename = cls._filename(filename_prefix)
      lines, _ = cls._read_lines_from_file(filename)
      # Strip wrapping single quotes
      vocab_list = [line[1:-1] for line in lines]
      return cls(vocab_list=vocab_list)
docs: Extracts list of subwords from file.