code: def sensitivity_index_calc(TPR, FPR):
      """
      Calculate Sensitivity index (d prime).
  
      :param TPR: sensitivity, recall, hit rate, or true positive rate
      :type TPR: float
      :param FPR: fall-out or false positive rate
      :type FPR: float
      :return: sensitivity index as float
      """
      try:
          return normal_quantile(TPR) - normal_quantile(FPR)
      except 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 1 for calling a global function with example usage: sensitivity_index_calc(TPR, FPR) and returns: unknown, str