class_docstr: A unittest class for testing the ClassLabels postprocessor.
code: def setUpClass(cls):
      (x_train, y_train), (x_test, y_test), _, _ = load_dataset("mnist")
      cls.mnist = (x_train, y_train), (x_test, y_test)
  
file_path: adversarial-robustness-toolbox/tests/defences/test_class_labels.py
imports: import logging
  import unittest
  import numpy
  from art.utils import load_dataset
  from art.defences.postprocessor import ClassLabels
  from tests.utils import master_seed, get_image_classifier_kr_tf, get_image_classifier_kr_tf_binary
label_desc: Use image node_id 1 for calling the TestClassLabels obj's underlying member method code with example usage: obj.setUpClass(cls) without return types