code: func MakeError(err error) *Error {
  	if err == nil {
  		return nil
  	}
  
  	return &Error{
  		GrpcCode:  int32(grpcutil.Code(err)),
  		Transient: transient.Tag.In(err),
  	}
  }
docs: // MakeError returns an Error object for err. If err is a wrapped gRPC error,
  // its code will be extracted and embedded in the returned Error.
  //
  // The Msg field will not be populated.