message: [TF 2.0 API Docs] tf.image.image_gradients
  Added usage example for image_gradients. The issue is raised in the link
diff: @@ -3404,6 +3404,43 @@ def image_gradients(image):
  Pair of tensors (dy, dx) holding the vertical and horizontal image
  gradients (1-step finite difference).
  + Usage Example:
  + ```python
  + BATCH_SIZE = 1
  + IMAGE_HEIGHT = 5
  + IMAGE_WIDTH = 5
  + CHANNELS = 1
  + image = tf.reshape(tf.range(IMAGE_HEIGHT * IMAGE_WIDTH * CHANNELS,
  + delta=1, dtype=tf.float32),
  + shape=(BATCH_SIZE, IMAGE_HEIGHT, IMAGE_WIDTH, CHANNELS))
  + dx, dy = tf.image.image_gradients(image)
  + print(image[0, :,:,0])
  + print('-' * 20)
  + print(dx[0, :,:,0])
  + print('-' * 20)
  + print(dy[0, :,:,0])
  + tf.Tensor(
  + [[ 0. 1. 2. 3. 4.]
  + [ 5. 6. 7. 8. 9.]
  + [10. 11. 12. 13. 14.]
  + [15. 16. 17. 18. 19.]
  + [20. 21. 22. 23. 24.]], shape=(5, 5), dtype=float32)
  + --------------------
  + tf.Tensor(
  + [[5. 5. 5. 5. 5.]
  + [5. 5. 5. 5. 5.]
  + [5. 5. 5. 5. 5.]
  + [5. 5. 5. 5. 5.]
  + [0. 0. 0. 0. 0.]], shape=(5, 5), dtype=float32)
  + --------------------
  + tf.Tensor(
  + [[1. 1. 1. 1. 0.]
  + [1. 1. 1. 1. 0.]
  + [1. 1. 1. 1. 0.]
  + [1. 1. 1. 1. 0.]
  + [1. 1. 1. 1. 0.]], shape=(5, 5), dtype=float32)
  + ```
  +
  Raises:
  ValueError: If `image` is not a 4D tensor.
  """
  