*   When using mixed precision, calling `RMSprop.apply_gradients` or
        `Nadam.apply_gradients` outside a `tf.function` does not work and will
        raise the AttributeError "Tensor.op is meaningless when eager execution
        is enabled". See this
        [issue](https://github.com/tensorflow/tensorflow/issues/45536) for
        details and a workaround.

## Bug Fixes and Other Changes