@Override
    public Node toNode() {
        NodeMapper mapper = new NodeMapper();
        mapper.disableToNodeForClass(Deprecated.class);
        return mapper.serialize(this);
    }
Gets the deprecated since value.

@return returns the optional deprecated since value.
smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/language/syntax/parameters/Deprecated.java