@Override
    public Model transform(TransformContext context) {
        Model model = context.getModel();
        return context.getTransformer().flattenAndRemoveMixins(model);
    }
{@code flattenAndRemoveMixins} flattens mixins out of the model.
smithy-build/src/main/java/software/amazon/smithy/build/transforms/FlattenAndRemoveMixins.java