message: Change `input` and `output` kwargs with default value None to required args in Functional model.
diff: @@ -93,9 +93,9 @@ class Functional(training_lib.Model):
  Args:
  inputs: List of input tensors (must be created via `tf.keras.Input()`).
  - outputs: List of outputs tensors.
  + outputs: List of output tensors.
  name: String, optional. Name of the model.
  - trainable: Boolean, whether the model's variables should be trainable.
  + trainable: Boolean, optional. If the model's variables should be trainable.
  """
  # See tf.Module for the usage of this property.
  @@ -108,7 +108,7 @@ class Functional(training_lib.Model):
  ))
  @trackable.no_automatic_dependency_tracking
  - def __init__(self, inputs=None, outputs=None, name=None, trainable=True,
  + def __init__(self, inputs, outputs, name=None, trainable=True,
  **kwargs):
  # This is used by the Model class, since we have some logic to swap the
  # class in the __new__ method, which will lead to __init__ get invoked
  