code: def backend_check_membership_accuracy(
      attack, dataset, attack_train_ratio, approx, use_label=True
  ):
      (x_train, y_train), (x_test, y_test) = dataset
      attack_train_size = int(len(x_train) * attack_train_ratio)
      attack_test_size = int(len(x_test) * attack_train_ratio)
  
      # train attack model using only attack_train_ratio of data
      if use_label:
          attack.fit(
              x_train[:attack_train_size],
              y_train[:attack_train_size],
              x_test[:attack_test_size],
              y_test[:attack_test_size],
          )
          # infer attacked feature on remainder of data
          inferred_train = attack.infer(
              x_train[attack_train_size:], y_train[attack_train_size:]
          )
          inferred_test = attack.infer(
              x_test[attack_test_size:], y_test[attack_test_size:]
          )
      else:
          attack.fit(
              x_train[:attack_train_size],
              test_x=x_test[:attack_test_size],
          )
          # infer attacked feature on remainder of data
          inferred_train = attack.infer(x_train[attack_train_size:])
          inferred_test = attack.infer(x_test[attack_test_size:])
  
      # check accuracy
      backend_check_accuracy(inferred_train, inferred_test, approx)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import pytest
  import numpy
  import keras
  from art.attacks.inference.membership_inference.black_box import MembershipInferenceBlackBox
  from art.estimators.classification.keras import KerasClassifier
  from art.estimators.estimator import BaseEstimator
  from art.estimators.classification.classifier import ClassifierMixin
  from art.estimators.regression import ScikitlearnRegressor, RegressorMixin
  from tests.attacks.utils import backend_test_classifier_type_check_fail
  from tests.utils import ARTTestException
label_desc: Use image node_id 21 for calling a global function with example usage: backend_check_membership_accuracy(attack, dataset, attack_train_ratio, approx, use_label) without return types