code: func newTransactionQuery(query *query, tx *Transaction) *TransactionQuery {
  	return &TransactionQuery{
  		query: query,
  		tx:    tx,
  	}
  }
docs: // newTransactionQuery creates and returns a new TransactionQuery. It is an
  // internal function that allows us to convert a Query to a TransactionQuery.
  // That way, there is only one canonical implementation of the query finisher
  // methods (e.g. Run, RunOne, IDs).