code: def test_4fold(self):
      train_info = self._write_tfrecord("train", 5, "abcdefghijkl")
      instructions = [
          splits.ReadInstruction("train", from_=k, to=k + 25, unit="%")
          for k in range(0, 100, 25)
      ]
      tests = self.reader.read(
          instructions=instructions,
          split_infos=[train_info],
      )
      instructions = [
          (
              splits.ReadInstruction("train", to=k, unit="%")
              + splits.ReadInstruction("train", from_=k + 25, unit="%")
          )
          for k in range(0, 100, 25)
      ]
      trains = self.reader.read(
          instructions=instructions,
          split_infos=[train_info],
      )
      read_tests = [list(r) for r in tfds.as_numpy(tests)]
      read_trains = [list(r) for r in tfds.as_numpy(trains)]
      self.assertEqual(
          read_tests,
          [
              [b"a", b"b", b"c"],
              [b"d", b"e", b"f"],
              [b"g", b"h", b"i"],
              [b"j", b"k", b"l"],
          ],
      )
      self.assertEqual(
          read_trains,
          [
              [b"d", b"e", b"f", b"g", b"h", b"i", b"j", b"k", b"l"],
              [b"a", b"b", b"c", b"g", b"h", b"i", b"j", b"k", b"l"],
              [b"a", b"b", b"c", b"d", b"e", b"f", b"j", b"k", b"l"],
              [b"a", b"b", b"c", b"d", b"e", b"f", b"g", b"h", b"i"],
          ],
      )
  
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 10 for calling the ReaderTest obj's underlying member method code with example usage: obj.test_4fold() without return types