message: Add Usage Example to Keras Nadam Optimizer
diff: @@ -59,6 +59,17 @@ class Nadam(optimizer_v2.OptimizerV2):
  References
  See [Dozat, T., 2015](http://cs229.stanford.edu/proj2015/054_report.pdf).
  +
  + Usage Example:
  + ```python
  + >>> import tensorflow as tf
  + >>> model = tf.keras.models.Sequential()
  + >>> model.add(tf.keras.layers.Dense(12, activation="relu"))
  + >>> model.add(tf.keras.layers.Dense(8, activation="relu"))
  + >>> model.add(tf.keras.layers.Dense(1, activation="sigmoid"))
  + >>> model.compile(optimizer=tf.keras.optimizers.Nadam(),
  + ... loss="binary_crossentropy")
  + ```
  """
  def __init__(self,
  