I'm adding serialization & saving support to the new FeatureSpace structure data processing utility: https://github.com/keras-team/keras/pull/17355/files
Add serialization support to FeatureSpace. by copybara-service · Pull Request #17355 · keras-team/keras

Add serialization support to FeatureSpace.

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I was happy that it was this easy to do. I didn't even have to make it a Model or a Layer (though I did make it a layer for a separate reason -- to make sure a subclassed layer could own a FeatureSpace and have it tracked for later saving)