code: def test_download_and_prepare(self):
      expected_num_examples = len(get_test_dummy_examples())
      with tempfile.TemporaryDirectory() as tmp_cache_dir:
          builder = DummyBeamDataset(
              cache_dir=tmp_cache_dir, beam_runner="DirectRunner"
          )
          builder.download_and_prepare()
          self.assertTrue(
              os.path.exists(
                  os.path.join(
                      tmp_cache_dir,
                      builder.name,
                      "default",
                      "0.0.0",
                      f"{builder.name}-train.arrow",
                  )
              )
          )
          self.assertDictEqual(
              builder.info.features,
              datasets.Features({"content": datasets.Value("string")}),
          )
          dset = builder.as_dataset()
          self.assertEqual(
              dset["train"].num_rows, expected_num_examples
          )
          self.assertEqual(
              dset["train"].info.splits["train"].num_examples,
              expected_num_examples,
          )
          self.assertDictEqual(
              dset["train"][0], get_test_dummy_examples()[0][1]
          )
          self.assertDictEqual(
              dset["train"][expected_num_examples - 1],
              get_test_dummy_examples()[expected_num_examples - 1][1],
          )
          self.assertTrue(
              os.path.exists(
                  os.path.join(
                      tmp_cache_dir,
                      builder.name,
                      "default",
                      "0.0.0",
                      "dataset_info.json",
                  )
              )
          )
          del dset
  
imports: import os
  import tempfile
  from functools import partial
  from unittest import TestCase
  from unittest.mock import patch
  import datasets
  import datasets.config
  from .utils import require_beam
label_desc: Use image node_id 1 for calling the BeamBuilderTest obj's underlying member method code with example usage: obj.test_download_and_prepare() without return types