code: def _filename_template(
      self, split: str
  ) -> naming.ShardedFileTemplate:
      return naming.ShardedFileTemplate(
          dataset_name="mnist",
          split=split,
          filetype_suffix="tfrecord",
          data_dir=self.tmp_dir,
      )
  
imports: import functools
  import itertools
  import os
  from unittest import mock
  import tensorflow
  import tensorflow_datasets
  from tensorflow_datasets import testing
  from tensorflow_datasets.core import example_parser
  from tensorflow_datasets.core import naming
  from tensorflow_datasets.core import reader
  from tensorflow_datasets.core import splits
  from tensorflow_datasets.core import writer
  from tensorflow_datasets.core.utils import read_config
  from tensorflow_datasets.core.utils import shard_utils
label_desc: Use image node_id 2 for calling the ReaderTest obj's underlying member method code with example usage: obj._filename_template(split) and returns: naming