@Override
    public Node toNode() {
        ObjectNode.Builder node = ObjectNode.builder();
        if (builtIn != null) {
            node.withMember(BUILT_IN, builtIn);
        }
        node.withMember(REQUIRED, required);
        if (defaultValue != null) {
            node.withMember(DEFAULT, defaultValue);
        }
        if (deprecated != null) {
            node.withMember(DEPRECATED, deprecated);
        }
        if (documentation != null) {
            node.withMember(DOCUMENTATION, documentation);
        }
        node.withMember(TYPE, type.toString());
        return node.build();
    }
Gets the parameter's default value.

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