computeWithDatabase<T>  method 
See SqliteReadContext.computeWithDatabase.
When called here directly on the connection, the call is wrapped in a write transaction.
Implementation
@override
Future<T> computeWithDatabase<T>(
    Future<T> Function(sqlite.Database db) compute) {
  return writeTransaction((tx) async {
    return tx.computeWithDatabase(compute);
  });
}