protected DeleteVersionsNode getDeepCopy() {
      DeleteVersionsNode node = new DeleteVersionsNode(ts, mvcc);
      for (Map.Entry<Long, SortedSet<Long>> e : deletesMap.entrySet()) {
        node.deletesMap.put(e.getKey(), new TreeSet<>(e.getValue()));
      }
      for (Map.Entry<Long, SortedSet<Long>> e : mvccCountingMap.entrySet()) {
        node.mvccCountingMap.put(e.getKey(), new TreeSet<>(e.getValue()));
      }
      return node;
    }
A data structure which contains infos we need that happens before this node's mvcc and after
the previous node's mvcc. A node means there is a version deletion at the mvcc and ts.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/querymatcher/NewVersionBehaviorTracker.java