code: def test_mnist_download(tmpdir):
      """Demonstrates that MNIST download works, using only the 'test' data. Assumes data does not change often."""
      o = download_mnist_data(tmpdir, train=False)
      assert 10000 == len(o)
      assert o[0][1] == 7
      assert o[len(o) - 1][1] == 6
  
file_path: petastorm/examples/mnist/tests/test_pytorch_mnist.py
imports: import logging
  import os
  import unittest
  import pyarrow
  import torch
  import pytest
  import examples.mnist.pytorch_example
  from examples.mnist.generate_petastorm_mnist import mnist_data_to_petastorm_dataset, download_mnist_data
  from examples.mnist.tests.conftest import SMALL_MOCK_IMAGE_COUNT
  from petastorm import make_reader, TransformSpec
label_desc: Use image node_id 3 for calling a global function with example usage: test_mnist_download(tmpdir) without return types