code: def joint_entropy_calc(classes, table, POP):
      
      try:
          result = 0
          for i in classes:
              for index, j in enumerate(classes):
                  p_prime = table[i][j] / POP[i]
                  if p_prime != 0:
                      result += p_prime * math.log(p_prime, 2)
          return -result
      except Exception:
          return "None"
docs: Calculate joint entropy.
  
      :param classes: confusion matrix classes
      :type classes : list
      :param table: confusion matrix table
      :type table : dict
      :param POP: population
      :type POP : dict
      :return: joint entropy as float