code: def TTPN_calc(item1, item2):
      """
      Calculate TPR, TNR, PPV, and NPV.
  
      :param item1: item1 in fractional expression
      :type item1: int
      :param item2: item2 in fractional expression
      :type item2: int
      :return: result as float
      """
      try:
          result = item1 / (item1 + item2)
          return result
      except (ZeroDivisionError, TypeError):
          return "None"
  
imports: from __future__ import division
  import math
  from .pycm_util import normal_quantile
  from .pycm_interpret import *
  from .pycm_param import CLASS_PARAMS
label_desc: Use image node_id 10 for calling a global function with example usage: TTPN_calc(item1, item2) and returns: result, str