code: func Send(ctx context.Context, err error) error {
  	meta, ok := metadata.FromIncomingContext(ctx)
  	if !ok {
  		meta = metadata.New(nil)
  	}
  	if trace.IsDebug() {
  		SetDebugInfo(err, meta)
  	}
  	if len(meta) != 0 {
  		sendErr := grpc.SendHeader(ctx, meta)
  		if sendErr != nil {
  			return trace.NewAggregate(err, sendErr)
  		}
  	}
  	return ToGRPC(err)
  }
docs: // Send is a high level function that:
  // * converts error to GRPC error
  // * attaches debug metadata to existing metadata if possible
  // * sends the header to GRPC