docs: private void commitTransactions() throws IOException {
        try {
           tm.commit();
        }
        catch (Exception e) {
           log.unableToCommitTransaction(e);
           throw new IOException("SharedLuceneLock could not commit a transaction", e);
        }
        if (trace) {
           log.tracef("Batch transaction committed for index: %s", indexName);
        }
     }