Calculate IS (Information score).

    :param TP: true positive
    :type TP : int
    :param FP: false positive
    :type FP : int
    :param FN: false negative
    :type FN : int
    :param POP: population
    :type POP : int
    :return: IS as float

def IS_calc(TP, FP, FN, POP):
    """
    Calculate IS (Information score).

    :param TP: true positive
    :type TP : int
    :param FP: false positive
    :type FP : int
    :param FN: false negative
    :type FN : int
    :param POP: population
    :type POP : int
    :return: IS as float
    """
    try:
        result = -math.log(((TP + FN) / POP), 2) + \
            math.log((TP / (TP + FP)), 2)
        return result
    except Exception:
        return "None"