code: def Eyraud_calc(TP, FP, FN, TN):
      """
      Calculate Eyraud similarity.
  
      :param TP: true positive
      :type TP: int
      :param TN: true negative
      :type TN: int
      :param FP: false positive
      :type FP: int
      :param FN: false negative
      :type FN: int
      :return: Eyraud similarity as float
      """
      try:
          part1 = (TP + FP) * (TP + FN)
          part2 = (TN + FP) * (TN + FN)
          return (TP - part1) / (part1 * part2)
      except Exception:
          return "None"
  
imports: from __future__ import division
  from enum import Enum
  import math
label_desc: Use image node_id 35 for calling a global function with example usage: Eyraud_calc(TP, FP, FN, TN) and returns: unknown, str