code: public static void addToHadoopConfiguration(Configuration conf) {
      final String SERIALIZATION_KEY = "io.serializations";
  
      String existingSerializers = conf.get(SERIALIZATION_KEY);
      if (existingSerializers != null) {
        conf.set(SERIALIZATION_KEY, existingSerializers + "," + WritableShimSerialization.class.getName());
      } else {
        conf.set(SERIALIZATION_KEY,
            "org.apache.hadoop.io.serializer.WritableSerialization," + WritableShimSerialization.class.getName());
      }
    }
docs: Helper method to add this serializer to an existing Hadoop config.