protected static function getApiKey($customApiKey=null)
	{
		//check if key was provided
		if ($customApiKey !== null) return $customApiKey;

		//otherwise lookup the key in the params or throw exception
		if (!isset(Yii::$app->params['api.google.key'])) {
			$msg = Yii::t('app', 'You need to set the google api key into your params (index: `api.google.key`)');
			throw new InvalidConfigException($msg);
		}

		return Yii::$app->params['api.google.key'];
	}