How to use the siuba.sql.translate.RankOver function in siuba

def _sql_rank(col, na_option, func_name, partition = False):
    rank_func = getattr(sql.func, func_name)

    if na_option == "keep":
        return _sql_rank_over(rank_func, col, partition = partition)

    warn_arg_default(func_name, 'na_option', None, "keep")

    return RankOver(rank_func(), order_by = col)

def _nth_sql(x, n, order_by = None, default = None) -> ClauseElement:
    if default is not None:
        raise NotImplementedError("default argument not implemented")

    if n < 0 and order_by is not None:
        # e.g. -1 in python is 0, -2 is 1
        n = abs(n + 1)
        order_by = order_by.desc()


    return RankOver(sql.func.nth_value(x, n + 1), order_by = order_by)

def _sql_rank_over(rank_func, col, partition):
    # partitioning ensures aggregates that use total length are correct
    # e.g. percent rank, cume_dist and friends
    over_clause = RankOver(
            rank_func(),
            order_by = col,
            partition_by = col.isnot(None) if partition else None
            )

    return sql.case({col.isnot(None): over_clause})

    return lambda col: RankOver(sa_func(), order_by = col)