@Override
        public AttributeValue getProperty(String key) {
            if (key.equals("version")) {
                return AttributeValue.literal(service.getVersion());
            } else if (key.equals("id")) {
                return AttributeValue.id(service.getId());
            } else {
                throw new SelectorException("Invalid nested 'service' selector attribute property: " + key);
            }
        }
Attribute that contains service shape properties.
smithy-model/src/main/java/software/amazon/smithy/model/selector/AttributeValueImpl.java