code: func (f *AccessLogFields) Keep(field string) bool {
  	defaultKeep := true
  	if f != nil {
  		defaultKeep = checkFieldValue(f.DefaultMode, defaultKeep)
  
  		if v, ok := f.Names[field]; ok {
  			return checkFieldValue(v, defaultKeep)
  		}
  	}
  	return defaultKeep
  }
docs: // Keep check if the field need to be kept or dropped