@Override
    public Node toNode() {
        return Node.objectNodeBuilder()
                .withMember(ENDPOINT, endpoint)
                .withOptionalMember(DUAL_STACK, Optional.ofNullable(dualStack).map(Node::from))
                .withOptionalMember(FIPS, Optional.ofNullable(fips).map(Node::from))
                .withOptionalMember(DUAL_STACK, Optional.ofNullable(dualStack).map(Node::from))
                .withOptionalMember(SIGNING_REGION, Optional.ofNullable(signingRegion).map(Node::from))
                .build();
    }
Gets the signing region.

@return Returns the signing region
smithy-aws-endpoints/src/main/java/software/amazon/smithy/rulesengine/aws/traits/RegionSpecialCase.java