message: Fix typos in tf.GradientTape documentation.
diff: @@ -681,8 +681,8 @@ class GradientTape(object):
  with tfe.GradientTape() as gg:
  gg.watch(x)
  y = x * x
  - dy_dx = gg.gradient(y, [x])[0] # Will compute to 6.0
  - d2y_dx2 = g.gradient(dy_dx, [x])[0] # Will compute to 2.0
  + dy_dx = gg.gradient(y, x) # Will compute to 6.0
  + d2y_dx2 = g.gradient(dy_dx, x) # Will compute to 2.0
  ```
  By default, the resources held by a GradientTape are released as soon as
  @@ -697,8 +697,8 @@ class GradientTape(object):
  g.watch(x)
  y = x * x
  z = y * y
  - dy_dx = g.gradient(z, [x])[0] # 6.0
  - dz_dx = g.gradient(y, [x])[0] # 108.0 (4*x^3 at x = 3)
  + dz_dx = g.gradient(z, x) # 108.0 (4*x^3 at x = 3)
  + dy_dx = g.gradient(y, x) # 6.0
  del g # Drop the reference to the tape
  """
  