@Nullable
  public Map<Integer, Set<Integer>> getTopology() {
    if (topologyUpdated.compareAndSet(true, false)) {
      return Collections.unmodifiableMap(topologyGraph);
    }
    return null;
  }
Wait for the specified RegionGroups to finish leader election.

@param regionGroupIds Specified RegionGroupIds
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/manager/load/cache/LoadCache.java