docs: def generate_strip_subparser(subparsers):
      """Adds a sub-command parser to `subparsers` to process prepared files
      for use with the tacl ngrams command."""
      parser = subparsers.add_parser(
          'strip', description=constants.STRIP_DESCRIPTION,
          epilog=constants.STRIP_EPILOG, formatter_class=ParagraphFormatter,
          help=constants.STRIP_HELP)
      parser.set_defaults(func=strip_files)
      utils.add_common_arguments(parser)
      parser.add_argument('input', help=constants.STRIP_INPUT_HELP,
                          metavar='INPUT')
      parser.add_argument('output', help=constants.STRIP_OUTPUT_HELP,
                          metavar='OUTPUT')