code: def test_cleanup(self):
      values = ["abcd", 91, {"x": "y"}]
      temp_dir = tempfile.mkdtemp()
      materializer = io_util.Materializer(temp_dir)
      with beam.Pipeline() as p:
          _ = p | beam.Create(values) | materializer.writer()
      self.assertNotEmpty(materializer._output_files())
      materializer.cleanup()
      self.assertEmpty(materializer._output_files())
      with self.assertRaisesRegex(
          ValueError, "Materializer must not be used after cleanup."
      ):
          materializer.reader()
  
file_path: data-validation/tensorflow_data_validation/utils/io_util_test.py
imports: import tempfile
  from absl.testing import absltest
  import apache_beam
  from tensorflow_data_validation.utils import io_util
label_desc: Use image node_id 2 for calling the MaterializerTest obj's underlying member method code with example usage: obj.test_cleanup() without return types