code: @Override
      public byte[] serialize() {
          try {
              ByteArrayOutputStream out = new ByteArrayOutputStream();
              ObjectOutputStream oos = new ObjectOutputStream(out);
              oos.writeObject(map);
              return out.toByteArray();
          } catch (IOException ex) {
              throw new IllegalStateException("Unable to compress SerializableMap");
          }
      }
docs: This serializes only the data, as opposed to the whole object.