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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def generate_diff_subparser(subparsers):
 """Adds a sub-command parser to `subparsers` to make a diff query."""

    parser = subparsers.add_parser(
        'diff', description=constants.DIFF_DESCRIPTION,
        epilog=constants.DIFF_EPILOG, formatter_class=ParagraphFormatter,
        help=constants.DIFF_HELP)
    parser.set_defaults(func=ngram_diff)
    group = parser.add_mutually_exclusive_group()
    group.add_argument('-a', '--asymmetric', help=constants.ASYMMETRIC_HELP,
                       metavar='LABEL')
    utils.add_common_arguments(parser)
    utils.add_db_arguments(parser)
    utils.add_corpus_arguments(parser)
    utils.add_query_arguments(parser)