public Optional<IntegrationResponse> getResponse(String statusCode) {
        return Optional.ofNullable(responses.get(statusCode));
    }
Get a specific integration response by status code expression.

@param statusCode Status code regular expression to search for.
@return Returns the optionally found response object.
smithy-aws-apigateway-traits/src/main/java/software/amazon/smithy/aws/apigateway/traits/MockIntegrationTrait.java