@Override
    public OperationObject updateOperation(
            Context<? extends Trait> context,
            OperationShape shape,
            OperationObject operation,
            String httpMethod,
            String path
    ) {
        IntegrationTraitIndex index = IntegrationTraitIndex.of(context.getModel());
        return index.getIntegrationTrait(context.getService(), shape)
                .map(trait -> operation.toBuilder()
                        .putExtension(INTEGRATION_EXTENSION_NAME, createIntegration(context, shape, trait))
                        .build())
                .orElseGet(() -> {
                    LOGGER.warning("No API Gateway integration trait found for " + shape.getId());
                    return operation;
                });
    }
Adds API Gateway integrations to operations.
smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddIntegrations.java