code: def ERR_calc(ACC):
      """
      Calculate Error rate.
  
      :param ACC: accuracy
      :type ACC: float
      :return: error rate as float
      """
      try:
          return 1 - ACC
      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 21 for calling a global function with example usage: ERR_calc(ACC) and returns: unknown, str