def _make_rank(fitness):
    """ make ranking according to fitness

    Arguments:
    ----------
        fitness {list[float]} -- each indivisuals' fitness

    Returns:
    --------
        rank {list[int]} -- rank

    Examples:
    ---------
        >>> fitness = [5, 3, 4, 1, 2]
        >>> rank = _make_rank(fitness)
        >>> rank
        [3, 4, 1, 2, 0]
    """
    rank_dict = {i: _fitness for i, _fitness in enumerate(fitness)}
    rank = []
    for k, _ in sorted(rank_dict.items(), key=lambda x: x[1]):
        rank.append(k)

    return rank