code: def macro_calc(item):
      """
      Calculate PPV_Macro, NPV_Macro, and TPR_Macro.
  
      :param item: True positive rate (TPR) or Positive predictive value (PPV)
      :type item:dict
      :return: PPV_Macro, NPV_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"
  
imports: from __future__ import division
  import math
  import operator
  from functools import reduce
  from .pycm_interpret import *
  from .pycm_ci import kappa_SE_calc, CI_calc, SE_calc
  from .pycm_util import complement
label_desc: Use image node_id 37 for calling a global function with example usage: macro_calc(item) and returns: unknown, str