public function get($serviceClassName)
    {
        if (false === $this->hasBeenInitialized) {
            throw new InitializationNotSetException(
                'You can get a service instance only when the service factory has been initialized.',
                1456419587
            );
        }

        if (false === $this->has($serviceClassName)) {
            throw new EntryNotFoundException(
                'The service "' . $serviceClassName . '" was not found in this service factory. Attach it before trying to get it!',
                1456419653
            );
        }

        return $this->serviceInstances[$serviceClassName];
    }