code: def IBA_calc(TPR, TNR, alpha=1):
      """
      Calculate Index of balanced accuracy (IBA).
  
      :param TNR: specificity or true negative rate
      :type TNR: float
      :param TPR: sensitivity, recall, hit rate, or true positive rate
      :type TPR: float
      :param alpha: alpha coefficient
      :type alpha: float
      :return: IBA as float
      """
      try:
          IBA = (1 + alpha * (TPR - TNR)) * TPR * TNR
          return IBA
      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 34 for calling a global function with example usage: IBA_calc(TPR, TNR, alpha) and returns: IBA, str