public void beginPersistentOutput() {
    if (persistentOutput) {
      return;
    }
    persistentOutput = true;
    firstTxn = true;
    if (outputJSON) {
      out.print("[");
    }
  }
enables output as a single, persistent list. at present, only relevant in the case of JSON
output.
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/WALPrettyPrinter.java