message: Add usage example for MaxPool2D
  Add usage example for MaxPool2D
diff: @@ -371,6 +371,12 @@ class MaxPooling2D(Pooling2D):
  [11.],
  [12.]]]], dtype=float32)>
  + Usage Example:
  +
  + >>> model = tf.keras.models.Sequential()
  + >>> model.add(tf.keras.layers.Conv2D(32, kernel_size=(3, 3), input_shape=(28,28,1)))
  + >>> model.add(tf.keras.layers.MaxPooling2D(pool_size=(2, 2)))
  +
  For example, for stride=(1,1) and padding="same":
  >>> x = tf.constant([[1., 2., 3.],
  