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