message: Added an example for history callback object.
diff: @@ -1108,6 +1108,19 @@ class History(Callback):
  This callback is automatically applied to
  every Keras model. The `History` object
  gets returned by the `fit` method of models.
  +
  + Example:
  +
  + >>> model = tf.keras.models.Sequential([tf.keras.layers.Dense(10)])
  + >>> model.compile(tf.keras.optimizers.SGD(), loss='mse')
  + >>> history = model.fit(np.arange(100).reshape(5, 20), np.zeros(5),
  + ... epochs=10)
  + >>> print(history.params)
  + {'verbose': 1, 'epochs': 10, 'steps': 1}
  + >>> # check the keys of history object
  + >>> print(history.history.keys())
  + dict_keys(['loss'])
  +
  """
  def __init__(self):
  