private Collection<HStore> getSpecificStores(List<byte[]> families) {
    Collection<HStore> specificStoresToFlush = new ArrayList<>();
    for (byte[] family : families) {
      specificStoresToFlush.add(stores.get(family));
    }
    return specificStoresToFlush;
  }
get stores which matches the specified families
@return the stores need to be flushed.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java