public Model flattenAndRemoveMixins(Model model) {
        return new FlattenAndRemoveMixins().transform(this, model);
    }
Flattens mixins out of the model and removes them from the model.

@param model Model to flatten.
@return Returns the flattened model.
smithy-model/src/main/java/software/amazon/smithy/model/transform/ModelTransformer.java