@Override
    protected Node createNode() {
        NodeMapper mapper = new NodeMapper();
        mapper.disableToNodeForClass(SpecificationExtensionTrait.class);
        mapper.setOmitEmptyValues(true);
        return mapper.serialize(this).expectObjectNode();
    }
Gets the specification extension header value in "as".

@return Returns the optionally present "as".
smithy-openapi-traits/src/main/java/software/amazon/smithy/openapi/traits/SpecificationExtensionTrait.java