@Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            } else if (!(o instanceof Reference)) {
                return false;
            }

            Reference reference = (Reference) o;
            return resource.equals(reference.resource)
                    && Objects.equals(ids, reference.ids)
                    && Objects.equals(service, reference.service)
                    && Objects.equals(rel, reference.rel);
        }
@return Gets the optional rel property.
smithy-model/src/main/java/software/amazon/smithy/model/traits/ReferencesTrait.java