message: added attribute error exception
  Raises attribute error when dtype is neither float nor integer type
diff: @@ -1731,9 +1731,16 @@ def convert_image_dtype(image, dtype, saturate=False, name=None):
  >> x = tf.random.normal(shape=(256, 256, 3), dtype=tf.float32)
  >> tf.image.convert_image_dtype(x, dtype=tf.float16, saturate=False)
  ```
  +
  + Raises:
  + AttributeError: Raises an attribute error when dtype is neither float nor integer
  """
  image = ops.convert_to_tensor(image, name='image')
  dtype = tf.dtypes.as_dtype(dtype)
  + if dtype.is_floating or dtype.is_integer:
  + pass
  + else:
  + raise AttributeError("dtype must be either floating point or integer")
  if dtype == image.dtype:
  return array_ops.identity(image, name=name)
  