@edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
      justification = "singleton pattern")
  public static NoOpRegionSizeStore getInstance() {
    return INSTANCE;
  }
A {@link RegionSizeStore} implementation that stores nothing.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/NoOpRegionSizeStore.java