public Map<ShapeId, ArnTrait> getServiceResourceArns(ToShapeId service) {
        return templates.getOrDefault(service.toShapeId(), Collections.emptyMap());
    }
Gets all of the mappings of resources within a service to its
arn trait.

@param service Service to retrieve.
@return Returns the mapping of resource ID to arn traits.
smithy-aws-traits/src/main/java/software/amazon/smithy/aws/traits/ArnIndex.java