code: def test_apply_fn_simple():
      add_two = functools.partial(add_number, increment=2)
      apply_fn = transform_lib.apply_fn(
          fn=add_two, input_feature="a", output_feature="c"
      )
      example = {"a": 1, "d": "left alone"}
      expected = [{"a": 1, "c": 3, "d": "left alone"}]
      assert list(apply_fn(example)) == expected
  
file_path: datasets/tensorflow_datasets/core/transform/transform_lib_test.py
imports: import functools
  from typing import Iterator
  import pytest
  from tensorflow_datasets.core.transform import transform_lib
label_desc: Use image node_id 4 for calling a global function with example usage: test_apply_fn_simple() without return types