code: func NewMockTransactionHeader(channelID string) (fab.TransactionHeader, error) {
  	user := mspmocks.NewMockSigningIdentity("test", "Org1MSP")
  
  	// generate a random nonce
  	nonce, err := crypto.GetRandomNonce()
  	if err != nil {
  		return nil, err
  	}
  
  	creator, err := user.Serialize()
  	if err != nil {
  		return nil, err
  	}
  
  	h := sha256.New()
  	id, err := computeTxnID(nonce, creator, h)
  	if err != nil {
  		return nil, err
  	}
  
  	txnID := MockTransactionHeader{
  		MockID:        fab.TransactionID(id),
  		MockCreator:   creator,
  		MockNonce:     nonce,
  		MockChannelID: channelID,
  	}
  
  	return &txnID, nil
  }
docs: // NewMockTransactionHeader creates mock TxnID based on mock user.