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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def macro_calc(item):
 """ Calculate PPV_Macro and TPR_Macro. :param item: PPV or TPR :type item:dict :return: PPV_Macro or TPR_Macro as float """

    try:
        item_sum = sum(item.values())
        item_len = len(item.values())
        return item_sum / item_len
    except Exception:
        return "None"