Map<byte[], Long> resetHighest() {
    Map<byte[], Long> old = this.highestSequenceIds;
    this.highestSequenceIds = new HashMap<>();
    return old;
  }
Reset the accounting of highest sequenceid by regionname.
@return Return the previous accounting Map of regions to the last sequence id written into
        each.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceIdAccounting.java