code: def _test_ratings(self, dataset_fn: Callable) -> None:
      ratings_row_count = 100
      with self._create_root(ratings_row_count) as tmpdir:
          dataset = dataset_fn(tmpdir)
          for sample in dataset:
              self._validate_sample(
                  sample,
                  self.DEFAULT_RATINGS_COLUMN_NAMES,
                  self.DEFAULT_RATINGS_COLUMN_TYPES,
              )
          self.assertEqual(len(list(dataset)), ratings_row_count)
  
imports: import contextlib
  import csv
  import os
  import random
  import tempfile
  import unittest
  from typing import Any, Callable, Dict, Generator, Iterable, List, Type, Union
  from torchrec.datasets.movielens import movielens_20m, movielens_25m
label_desc: Use image node_id 6 for calling the MovieLensTest obj's underlying member method code with example usage: obj._test_ratings(dataset_fn) without return types