Calculate overall accuracy.

    :param TP: true positive
    :type TP : dict
    :param POP: population
    :type POP:int
    :return: overall_accuracy as float

def overall_accuracy_calc(TP, POP):
    """
    Calculate overall accuracy.

    :param TP: true positive
    :type TP : dict
    :param POP: population
    :type POP:int
    :return: overall_accuracy as float
    """
    try:
        overall_accuracy = sum(TP.values()) / POP
        return overall_accuracy
    except Exception:
        return "None"