def add_options(_parser):
    """
    Adds options to the passed in '_parser'

    :type _parser: OptionParser instance
    :param _parser: passed in parser

    :rtype: None
    :return: None
    """
    _parser.add_option('-y', '--year', dest='year', action='store', help=
        'Year for the merge')
    _parser.add_option('-m', '--month', dest='month', action='store', help=
        'Month for the merge')
    _parser.add_option('-d', '--day', dest='day', action='store', help=
        'Day for the merge')
    _parser.add_option('-D', '--directory', dest='directory', action=
        'store', help='Directory containing files to merge')
    _parser.add_option('-f', '--file', dest='file', action='store', help=
        'File containing list of input directories')
    _parser.add_option('-w', '--window', dest='window', action='store',
        help='Window in days (merge for the past *n* days')
    _parser.add_option('-l', '--lookback', dest='lookback', action='store',
        help='Lookback period (merge for 1 day *n* days prior)')
    _parser.add_option('-t', '--topic', dest='topic', action='store', help=
        'Topic for the merge')
    _parser.add_option('-i', '--input-prefix', dest='input_prefix', action=
        'store', help='Input directory prefix')
    _parser.add_option('-o', '--output-prefix', dest='output_prefix',
        action='store', help='Output directory prefix')
    _parser.add_option('-n', '--num-reducers', dest='num_reducers', action=
        'store', help='Number of reducers')
    _parser.add_option('-c', '--codec', dest='codec', action='store', help=
        'Compression codec to use')
    _parser.add_option('-q', '--queue', dest='queue', action='store', help=
        'Mapreduce job queue')
    _parser.add_option('-r', '--dry-run', dest='dry_run', action=
        'store_true', default=False, help=
        'Dry run; create, but dont execute the Pig script')
