code: func (txPvtRwSet *TxPvtRwSet) toProtoMsg() (*rwset.TxPvtReadWriteSet, error) {
  	protoMsg := &rwset.TxPvtReadWriteSet{DataModel: rwset.TxReadWriteSet_KV}
  	var nsProtoMsg *rwset.NsPvtReadWriteSet
  	var err error
  	for _, nsPvtRwSet := range txPvtRwSet.NsPvtRwSet {
  		if nsProtoMsg, err = nsPvtRwSet.toProtoMsg(); err != nil {
  			return nil, err
  		}
  		protoMsg.NsPvtRwset = append(protoMsg.NsPvtRwset, nsProtoMsg)
  	}
  	return protoMsg, nil
  }
docs: ///////////////////////////////////////////////////////////////////////////////
  // functions for private read-write set
  ///////////////////////////////////////////////////////////////////////////////