message: Added usage example for tf.keras.callbacks.TensorBoard
diff: @@ -1460,6 +1460,11 @@ class TensorBoard(Callback):
  You can find more information about TensorBoard
  [here](https://www.tensorflow.org/get_started/summaries_and_tensorboard).
  + Example:
  + >>>tensorboard_callback = tf.keras.callbacks.TensorBoard(log_dir="./logs")
  + >>>model.fit(x_train, y_train, epochs=2, callbacks=[tensorboard_callback])
  + >>>#run the tensorboard command to view the visualizations
  +
  Arguments:
  log_dir: the path of the directory where to save the log files to be
  parsed by TensorBoard.
  