private function getAdapterClassFromArgument($argument)
    {
        if (!class_exists($adapterClass = $argument) &&
            !class_exists($adapterClass = '\\Sly\\NotificationPusher\\Adapter\\' . ucfirst($argument))) {
            throw new AdapterException(
                sprintf(
                    'Adapter class %s does not exist',
                    $adapterClass
                )
            );
        }

        return $adapterClass;
    }