@Override
  protected boolean canBeFlattened() {
    return true;
  }
------------------------------------------------------------------------ Copy C-tor to be used
when new CSLMImmutableSegment is being built from a Mutable one. This C-tor should be used when
active MutableSegment is pushed into the compaction pipeline and becomes an ImmutableSegment.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/CSLMImmutableSegment.java