<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def generate_statistics_subparser(subparsers):
 """Adds a sub-command parser to `subparsers` to generate statistics from a set of results."""

    parser = subparsers.add_parser(
        'stats', description=constants.STATISTICS_DESCRIPTION,
        formatter_class=ParagraphFormatter, help=constants.STATISTICS_HELP)
    parser.set_defaults(func=generate_statistics)
    utils.add_common_arguments(parser)
    utils.add_corpus_arguments(parser)
    parser.add_argument('results', help=constants.STATISTICS_RESULTS_HELP,
                        metavar='RESULTS')