def _get_date_parse_fn(target):
    """get date parse function

    This method is used to parse date arguments as target type.

    Example:
        get_date_parse_fn('20120101')('2017-01-01') => '20170101'
        get_date_parse_fn(20120101)('2017-01-01') => 20170101
    """
    if isinstance(target, int):
        _fn = lambda x: int(str(x).replace("-", "")[:8])  # 20200201
    elif isinstance(target, str) and len(target) == 8:
        _fn = lambda x: str(x).replace("-", "")[:8]  # '20200201'
    else:
        _fn = lambda x: x  # '2021-01-01'
    return _fn