code: def test_map(self):
      with tempfile.TemporaryDirectory() as tmp_dir:
          dsets = self._create_dummy_dataset_dict()
  
          mapped_dsets_1: DatasetDict = dsets.map(
              lambda ex: {"foo": ["bar"] * len(ex["filename"])},
              batched=True,
          )
          self.assertListEqual(
              list(dsets.keys()), list(mapped_dsets_1.keys())
          )
          self.assertListEqual(
              mapped_dsets_1["train"].column_names, ["filename", "foo"]
          )
  
          cache_file_names = {
              "train": os.path.join(tmp_dir, "train.arrow"),
              "test": os.path.join(tmp_dir, "test.arrow"),
          }
          mapped_dsets_2: DatasetDict = mapped_dsets_1.map(
              lambda ex: {"bar": ["foo"] * len(ex["filename"])},
              batched=True,
              cache_file_names=cache_file_names,
          )
          self.assertListEqual(
              list(dsets.keys()), list(mapped_dsets_2.keys())
          )
          self.assertListEqual(
              sorted(mapped_dsets_2["train"].column_names),
              sorted(["filename", "foo", "bar"]),
          )
          del dsets, mapped_dsets_1, mapped_dsets_2
  
imports: import os
  import tempfile
  from unittest import TestCase
  import numpy
  import pandas
  import pytest
  from datasets import load_from_disk
  from datasets.arrow_dataset import Dataset
  from datasets.dataset_dict import DatasetDict, IterableDatasetDict
  from datasets.features import ClassLabel, Features, Sequence, Value
  from datasets.iterable_dataset import IterableDataset
  from datasets.splits import NamedSplit
  from .utils import assert_arrow_memory_doesnt_increase, assert_arrow_memory_increases, require_tf, require_torch
label_desc: Use image node_id 17 for calling the DatasetDictTest obj's underlying member method code with example usage: obj.test_map() without return types