def reverse_dict(ori_dict):
    """Reverse dictionary mapping.

    Parameters
    ----------
    ori_dict : Dictionary
        original given dictionary

    Returns
    -------
    res_dict : Dictionary
        The result dictionary with the mapping of one-to-many
    """
    res_dict = {}
    for key in ori_dict:
        if ori_dict[key] not in res_dict:
            res_dict[ori_dict[key]] = [key]
        else:
            res_dict[ori_dict[key]].append(key)

    return res_dict