presto-kafka/src/main/java/io/prestosql/plugin/kafka/KafkaConnector.java/KafkaConnector/beginTransaction
class KafkaConnector:    @Override
    public ConnectorTransactionHandle beginTransaction(IsolationLevel isolationLevel, boolean readOnly)
    {
        checkConnectorSupports(READ_COMMITTED, isolationLevel);
        return KafkaTransactionHandle.INSTANCE;
    }