presto-local-file/src/main/java/io/prestosql/plugin/localfile/LocalFileConnector.java/LocalFileConnector/beginTransaction
class LocalFileConnector:    @Override
    public ConnectorTransactionHandle beginTransaction(IsolationLevel isolationLevel, boolean readOnly)
    {
        checkConnectorSupports(READ_COMMITTED, isolationLevel);
        return LocalFileTransactionHandle.INSTANCE;
    }