code: def test_mixup_empty_data(art_warning, empty_image, alpha, num_mix):
      try:
          mixup = Mixup(num_classes=10, alpha=alpha, num_mix=num_mix)
          x, y = mixup(empty_image, np.arange(len(empty_image)))
          assert_array_equal(x, empty_image)
          assert_array_almost_equal(
              y.sum(axis=1), np.ones(len(empty_image))
          )
      except ARTTestException as e:
          art_warning(e)
  
file_path: adversarial-robustness-toolbox/tests/defences/preprocessor/mixup/test_mixup.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import numpy
  import pytest
  from numpy.testing import assert_array_equal, assert_array_almost_equal
  from art.config import ART_NUMPY_DTYPE
  from art.defences.preprocessor import Mixup
  from tests.utils import ARTTestException
label_desc: Use image node_id 4 for calling a global function with example usage: test_mixup_empty_data(art_warning, empty_image, alpha, num_mix) without return types