code: def test_png_4chan_to_jpeg(self):
      image = self._get_image("6pixels_4chan.png")
      jpeg = image_utils.png_to_jpeg(image)
      self.assertIsInstance(jpeg, bytes)
      image_np_jpeg = image_utils.decode_image(jpeg)
      np.testing.assert_array_equal(image_np_jpeg, SIX_PIXELS_JPEG)
  
file_path: datasets/tensorflow_datasets/core/utils/image_utils_test.py
imports: import os
  import numpy
  import tensorflow
  from tensorflow_datasets import testing
  from tensorflow_datasets.core.utils import image_utils
label_desc: Use image node_id 4 for calling the ImageUtilsTest obj's underlying member method code with example usage: obj.test_png_4chan_to_jpeg() without return types