code: def url_infos(cls) -> Optional[Dict[str, download.checksums.UrlInfo]]:
      return {
          "http://data.org/file1.zip": download.checksums.UrlInfo(
              size=42,
              checksum="d45899d9a6a0e48afb250aac7ee3dc50e73e263687f15761d754515cd8284e0a",
              filename="file1.zip",
          ),
      }
  
imports: import contextlib
  import os
  import pathlib
  from typing import Dict, Iterator, List, Optional
  from unittest import mock
  from absl.testing import parameterized
  from etils import epath
  import pytest
  import tensorflow_datasets
  from tensorflow_datasets import testing
  from tensorflow_datasets.core import download
  from tensorflow_datasets.core import utils
  from tensorflow_datasets.core.utils import file_utils
  from tensorflow_datasets.scripts.cli import build
  from tensorflow_datasets.scripts.cli import main
label_desc: Use image node_id 2 for calling the DummyDatasetNoGenerate obj's underlying member method code with example usage: obj.url_infos(cls) and returns: dict