code: def GI_calc(AUC):
      """
      Calculate Gini index.
  
      :param AUC: Area under the ROC
      :type AUC: float
      :return: Gini index as float
      """
      try:
          return 2 * AUC - 1
      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 30 for calling a global function with example usage: GI_calc(AUC) and returns: unknown, str