public function registerService($name, $serviceId)
    {
        if (isset($this->serviceMap[$name])) {
            throw new \InvalidArgumentException(sprintf(
                '%s service "%s" is already registered',
                $this->serviceType, $name
            ));
        }

        $this->serviceMap[$name] = $serviceId;
        $this->services[$name] = null;
    }