code: def _validate_cache_files(self, cache_files, expected_size):
      # Checks the TFRecord file
      self.assertTrue(os.path.isfile(cache_files.tfrecord_files[0]))
      self.assertGreater(
          os.path.getsize(cache_files.tfrecord_files[0]), 0
      )
  
      # Checks the metadata file
      self.assertTrue(os.path.isfile(cache_files.metadata_file))
      self.assertGreater(os.path.getsize(cache_files.metadata_file), 0)
      metadata_dict = cache_files.load_metadata()
      self.assertEqual(metadata_dict["size"], expected_size)
  
imports: import hashlib
  import json
  import os
  import shutil
  from unittest import mock
  import tensorflow
  from mediapipe.model_maker.python.vision.core import test_utils
  from mediapipe.model_maker.python.vision.object_detector import dataset_util
  from mediapipe.tasks.python.test import test_utils
label_desc: Use image node_id 13 for calling the DatasetUtilTest obj's underlying member method code with example usage: obj._validate_cache_files(cache_files, expected_size) without return types