message: Update documentation to use proper tf.train.CheckpointOptions.
diff: @@ -2132,7 +2132,8 @@ class Checkpoint(tracking.AutoTrackable):
  # You can also pass options to read(). For example this
  # runs the IO ops on the localhost:
  - options = tf.CheckpointOptions(experimental_io_device="/job:localhost")
  + options = tf.train.CheckpointOptions(
  + experimental_io_device="/job:localhost")
  checkpoint.read(path, options=options)
  ```
  