public static EndpointModifierIndex of(Model model) {
        return model.getKnowledge(EndpointModifierIndex.class, EndpointModifierIndex::new);
    }
Locates the endpoint modifier traits applied to services.

Endpoint modifier traits are traits that are marked by {@link EndpointModifierTrait}
smithy-aws-endpoints/src/main/java/software/amazon/smithy/rulesengine/aws/traits/EndpointModifierIndex.java