docs: def generate_search_subparser(subparsers):
      """Adds a sub-command parser to `subparsers` to generate search
      results for a set of n-grams."""
      parser = subparsers.add_parser(
          'search', description=constants.SEARCH_DESCRIPTION,
          epilog=constants.SEARCH_EPILOG, formatter_class=ParagraphFormatter,
          help=constants.SEARCH_HELP)
      parser.set_defaults(func=search_texts)
      utils.add_common_arguments(parser)
      utils.add_db_arguments(parser)
      utils.add_corpus_arguments(parser)
      utils.add_query_arguments(parser)
      parser.add_argument('ngrams', help=constants.SEARCH_NGRAMS_HELP,
                          nargs='*', metavar='NGRAMS')