code: func (daemon *Daemon) mergeAndVerifyLogConfig(cfg *containertypes.LogConfig) error {
  	if cfg.Type == "" {
  		cfg.Type = daemon.defaultLogConfig.Type
  	}
  
  	if cfg.Config == nil {
  		cfg.Config = make(map[string]string)
  	}
  
  	if cfg.Type == daemon.defaultLogConfig.Type {
  		for k, v := range daemon.defaultLogConfig.Config {
  			if _, ok := cfg.Config[k]; !ok {
  				cfg.Config[k] = v
  			}
  		}
  	}
  
  	return logger.ValidateLogOpts(cfg.Type, cfg.Config)
  }
docs: // mergeLogConfig merges the daemon log config to the container's log config if the container's log driver is not specified.