code: func IsSuccess(err error, successCodes ...codes.Code) error {
  
  	// Shortcut the process by first checking to see if the error is nil.
  	if err == nil {
  		return nil
  	}
  
  	// Check to see if the provided error is an RPC error.
  	stat, ok := status.FromError(err)
  	if !ok {
  		return err
  	}
  
  	if stat.Code() == codes.OK {
  		return nil
  	}
  	for _, c := range successCodes {
  		if stat.Code() == c {
  			return nil
  		}
  	}
  
  	return err
  }
docs: // IsSuccess returns nil if the provided error is an RPC error with an error
  // code that is OK (0) or matches one of the additional, provided successful
  // error codes. Otherwise the original error is returned.