code: func createSubSentAndAckProto(sub *subState, r *subSentAndAck) []byte {
  	op := &spb.RaftOperation{
  		OpType: spb.RaftOperation_SendAndAck,
  		SubSentAck: &spb.SubSentAndAck{
  			Channel:  sub.subject,
  			AckInbox: sub.AckInbox,
  			Sent:     r.sent,
  			Ack:      r.ack,
  		},
  	}
  	data, err := op.Marshal()
  	if err != nil {
  		panic(err)
  	}
  	return data
  }
docs: // Little helper function to create a RaftOperation_SendAndAck protocol
  // and serialize it.