@InterfaceAudience.Private
  static Map<byte[], Algorithm> createFamilyCompressionMap(Configuration conf) {
    Map<byte[], String> stringMap = createFamilyConfValueMap(conf, COMPRESSION_FAMILIES_CONF_KEY);
    Map<byte[], Algorithm> compressionMap = new TreeMap<>(Bytes.BYTES_COMPARATOR);
    for (Map.Entry<byte[], String> e : stringMap.entrySet()) {
      Algorithm algorithm = HFileWriterImpl.compressionByName(e.getValue());
      compressionMap.put(e.getKey(), algorithm);
    }
    return compressionMap;
  }
Runs inside the task to deserialize column family to compression algorithm map from the
configuration.
@param conf to read the serialized values from
@return a map from column family to the configured compression algorithm
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/HFileOutputFormat2.java