code: def _check_sha256sum(self, download: DownloadableFile):
      if download._hashcode is not None:
          matches = re.findall(r"^[A-Fa-f0-9]{64}$", download._hashcode)
          assert (
              len(matches) == 1
          ), f"{download._url} doesn't have a valid sha256sum"
  
file_path: mmf/tests/configs/test_zoo_urls.py
imports: import re
  import time
  import typing
  import unittest
  from mmf.utils.configuration import load_yaml
  from mmf.utils.download import check_header, DownloadableFile
  from omegaconf import DictConfig, OmegaConf
  from tests.test_utils import skip_if_macos, skip_if_no_network
label_desc: Use image node_id 3 for calling the TestConfigsForKeys obj's underlying member method code with example usage: obj._check_sha256sum(download) without return types