public function getContentCss($configName = null)
    {
        if (is_null($configName)) {
            $configName = $this->ckEditorConfigManager->getDefaultConfig();
        }

        $configs = $this->ckEditorConfigManager->getConfigs();
        if (array_key_exists('contentsCss', $configs[$configName])) {
            return $configs[$configName]['contentsCss'];
        }

        return false;
    }