message: Fix bug in eager documentation.
  When implementing a custom layer, it's necessary to call the Layer constructor
  from the custom layer's constructor.
diff: @@ -149,16 +149,17 @@ it to implement your own layer:
  ```py
  class MySimpleLayer(tf.keras.layers.Layer):
  def __init__(self, output_units):
  + super(MySimpleLayer, self).__init__()
  self.output_units = output_units
  - def build(self, input):
  + def build(self, input_shape):
  # The build method gets called the first time your layer is used.
  # Creating variables on build() allows you to make their shape depend
  - # on the input shape and hence remove the need for the user to specify
  + # on the input shape and hence removes the need for the user to specify
  # full shapes. It is possible to create variables during __init__() if
  # you already know their full shapes.
  self.kernel = self.add_variable(
  - "kernel", [input.shape[-1], self.output_units])
  + "kernel", [input_shape[-1], self.output_units])
  def call(self, input):
  # Override call() instead of __call__ so we can perform some bookkeeping.
  