assumes layers only ever have one positional argument. This assumption
        doesn't hold true before TF 2.4 either, but is more likely to cause
        issues now.
    *   Code that manually enters `keras.backend.get_graph()` before building a
        functional model is no longer needed.
    *   Start enforcing input shape assumptions when calling Functional API
        Keras models. This may potentially break some users, in case there is a