code: func NewLoggerBase(conf *BaseConfig, log LoggerFunc) (*LoggerBase, error) {
  	if _, ok := levelNums[conf.Level]; !ok {
  		return nil, ErrBadLevel
  	}
  
  	if _, ok := levelNums[conf.StackLevel]; !ok {
  		return nil, ErrBadStackLevel
  	}
  
  	ctx := map[string]interface{}{}
  
  	return &LoggerBase{conf: conf, log: log, ctx: ctx}, nil
  }
docs: // NewLoggerBase creates a new LoggerBase.