private static Builder prepareBuilder(Builder builder) {
        // Always add a UniqueItems trait that is serialized when the set is serialized as a list for IDL v2.
        builder.addTrait(new UniqueItemsTrait(builder.getSourceLocation()));
        return builder;
    }
Represents a {@code set} shape.

<p>Sets are deprecated. Use list shapes with the uniqueItems trait instead.
When serialized using IDL v2, sets are converted to lists with the
uniqueItems trait.
smithy-model/src/main/java/software/amazon/smithy/model/shapes/SetShape.java