public Map<Integer, Pair<NodeStatistics, NodeStatistics>> getDifferentNodeStatisticsMap() {
    return Collections.unmodifiableMap(differentNodeStatisticsMap);
  }
NodeStatisticsChangeEvent represents the change of Node statistics.
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/manager/load/subscriber/NodeStatisticsChangeEvent.java