public Optional<Trait> getIntegrationTrait(ToShapeId service, ToShapeId shape) {
        return Optional.ofNullable(traits.getOrDefault(service.toShapeId(), MapUtils.of())
                .get(shape.toShapeId()));
    }
Get the integration trait for a particular operation, resource, or
service bound within a service.

@param service Service shape or ShapeId thereof.
@param shape Operation, service, or resource shape in the service.
 When the service shape ID is provided, the integration trait of the
 service is returned if present.

@return The integration trait or an empty optional if none set
smithy-aws-apigateway-traits/src/main/java/software/amazon/smithy/aws/apigateway/traits/IntegrationTraitIndex.java