message: Fix typo in test_image.py
diff: @@ -48,7 +48,7 @@ class ImageDatasetTest(test.TestCase):
  webp_contents = f.read()
  with self.cached_session():
  - png_op = image_ops.decode_png(png_contents, channels=channel)
  + png_op = image.decode_png(png_contents, channels=channel)
  png = png_op.eval()
  self.assertEqual(png.shape, (height, width, channel))
  