public Stream<Trait> addedTraits() {
        return traitDiff.values()
                .stream()
                .filter(pair -> pair.getLeft() == null)
                .map(Pair::getRight);
    }
Gets a stream of added traits.

@return Returns the traits that were added.
smithy-diff/src/main/java/software/amazon/smithy/diff/ChangedShape.java