function getRedisSentinelGroupName(sentinelName) {
  return sentinelName || require('config').get('redis.defaultSentinelGroup');
}
Get default Redis sentinel group name from config
 This method checks if a string is given as input and returns this, otherwise
 the default value from config files is used

 @param {string|null} sentinelName possible sentinel group name to use or null
 @return {string} default name from config for sentinel groups