code: func (e *Error) ToError() error {
  	if e == nil {
  		return nil
  	}
  
  	code := codes.Code(e.GrpcCode)
  	err := status.Errorf(code, "%s", e.Msg)
  	if e.Transient || grpcutil.IsTransientCode(code) {
  		err = transient.Tag.Apply(err)
  	}
  	return err
  }
docs: // ToError converts an Error into a gRPC error. If e is nil, a nil error will
  // be returned.