message: [TF 2.0 API Docs] tf.image.adjust_gamma
  Updated adjust_gamma by adding a usage example in the docstring in image_ops_impl.py. The issue has been raised and is provided in this link
diff: @@ -1664,6 +1664,12 @@ def adjust_gamma(image, gamma=1, gain=1):
  gain : A scalar or tensor. The constant multiplier.
  Returns:
  A Tensor. A Gamma-adjusted tensor of the same shape and type as `image`.
  + Usage Example:
  + ```python
  + >> import tensorflow as tf
  + >> x = tf.random.normal(shape=(256, 256, 3))
  + >> tf.image.adjust_gamma(x, 0.2)
  + ```
  Raises:
  ValueError: If gamma is negative.
  Notes:
  