@Override
    protected Node createNode() {
        return new ObjectNode(MapUtils.of(), getSourceLocation())
                .withOptionalMember("since", getSince().map(Node::from))
                .withOptionalMember("message", getMessage().map(Node::from));
    }
Gets the deprecation message value.

@return returns the optional deprecation message value.
smithy-model/src/main/java/software/amazon/smithy/model/traits/DeprecatedTrait.java