code: func (t *MockTransactor) CreateTransactionHeader(opts ...fab.TxnHeaderOpt) (fab.TransactionHeader, error) {
  	txh, err := txn.NewHeader(t.Ctx, t.ChannelID)
  	if err != nil {
  		return nil, errors.WithMessage(err, "new transaction ID failed")
  	}
  
  	return txh, nil
  }
docs: // CreateTransactionHeader creates a Transaction Header based on the current context.