@Override
      public void close(TaskAttemptContext c) throws IOException, InterruptedException {
        for (WriterLength wl : this.writers.values()) {
          close(wl.writer);
        }
      }
ExtendedCell and ExtendedCellSerialization are InterfaceAudience.Private. We expose this config
for internal usage in jobs like WALPlayer which need to use features of ExtendedCell.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/HFileOutputFormat2.java