private Collection<Shape> getTraitShapes(Model model, ShapeId traitId) {
        return getTraitShapes(model, traitId, new HashMap<>()).values();
    }
@param keepFilter Predicate that if matched keeps a trait definition from being unreferenced.
smithy-model/src/main/java/software/amazon/smithy/model/neighbor/UnreferencedTraitDefinitions.java