code: def testPng(self):
      # Read some real PNGs, converting to different channel numbers
      inputs = [(1, "lena_gray.png")]
      for channels_in, filename in inputs:
          for channels in 0, 1, 3, 4:
              with self.cached_session() as sess:
                  path = os.path.join(
                      prefix_path, "png", "testdata", filename
                  )
                  png0 = io_ops.read_file(path)
                  image0 = image_ops.decode_image(
                      png0, channels=channels
                  )
                  image1 = image_ops.decode_png(png0, channels=channels)
                  png0, image0, image1 = self.evaluate(
                      [png0, image0, image1]
                  )
                  self.assertEqual(
                      image0.shape, (26, 51, channels or channels_in)
                  )
                  self.assertAllEqual(image0, image1)
  
file_path: tensorflow/tensorflow/python/kernel_tests/image_ops/decode_image_op_test.py
imports: import os.path
  import numpy
  from tensorflow.python.framework import errors_impl
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import image_ops
  from tensorflow.python.ops import io_ops
  import tensorflow.python.ops.nn_grad
  from tensorflow.python.platform import test
label_desc: Use image node_id 4 for calling the DecodeImageOpTest obj's underlying member method code with example usage: obj.testPng() without return types