code: func isSecurityGroupNotFound(err error) bool {
  	errType := reflect.TypeOf(err).String()
  	errTypeSlice := strings.Split(errType, ".")
  	errTypeValue := ""
  	if len(errTypeSlice) != 0 {
  		errTypeValue = errTypeSlice[len(errTypeSlice)-1]
  	}
  	if errTypeValue == "ErrResourceNotFound" {
  		return true
  	}
  
  	return false
  }
docs: // isSecurityGroupNotFound return true while 'err' is object of gophercloud.ErrResourceNotFound