def LR_calc(item1, item2):
    """
    Calculate likelihood ratio.

    :param item1: item1 in expression
    :type item1:float
    :param item2: item2 in expression
    :type item2:float
    :return: LR+ and LR- as float
    """
    try:
        result = item1 / item2
        return result
    except Exception:
        return "None"