void putPotentiallyIntroducedTrait(ShapeId target, Trait trait) {
        if (potentiallyIntroducedTraits == null) {
            potentiallyIntroducedTraits = new HashMap<>();
        }

        Map<ShapeId, Trait> shapeUnclaimedTraits = potentiallyIntroducedTraits.computeIfAbsent(target,
                id -> new LinkedHashMap<>());
        shapeUnclaimedTraits.put(trait.toShapeId(), trait);
    }
Applies mixins to shapes after the mixins have been resolved.
smithy-model/src/main/java/software/amazon/smithy/model/loader/ApplyMixin.java