(SavedModelEstimator).
    *   Adds leaf index modes as an argument.
    *   Allow a different output shape from the input in
        tf.contrib.image.transform.
    *   Change the state_size order of the StackedRNNCell to be natural order.
        To keep the existing behavior, user can add reverse_state_order=True
        when constructing the StackedRNNCells.