docs: public synchronized void beginTransaction() throws TransactionInProgressException, TransactionAbortedException
      {
          if (isInTransaction())
          {
              throw new TransactionInProgressException("PersistenceBroker is already in transaction");
          }
          fireBrokerEvent(BEFORE_BEGIN_EVENT);
          setInTransaction(true);
          this.connectionManager.localBegin();
          fireBrokerEvent(AFTER_BEGIN_EVENT);
      }