def decide_on_key(k_decide, v_decide, config_dict):
    """ checks with old config file to decide on key in new config file. """
    if k_decide in config_dict[0]:
        v_decide.remove(k_decide)
        return k_decide, v_decide
    for kk, vv in config_dict.items():
        if k_decide in vv and kk in v_decide:
            v_decide.remove(kk)
            return kk, v_decide
    v_decide.remove(k_decide)
    return k_decide, v_decide
