message: use layer's input_spec for network
diff: @@ -587,16 +587,6 @@ class Network(base_layer.Layer):
  extra_variables=self._non_trainable_weights +
  self._trainable_weights))
  - @property
  - def input_spec(self):
  - """Gets the network's input specs.
  -
  - Returns:
  - A list of `InputSpec` instances (one per input to the model)
  - or a single instance if the model has only one input.
  - """
  - return
  -
  @generic_utils.default
  def build(self, input_shape):
  """Builds the model based on input shapes received.
  