@Override
  public void toData(DataOutput out,
      SerializationContext context) throws IOException {
    super.toData(out, context);
    DataSerializer.writeObject(key, out);
    DataSerializer.writeObject(cbArg, out);
    DataSerializer.writeObject(this.context, out);
    out.writeBoolean(returnTombstones);
  }
Empty constructor to satisfy {@link DataSerializer} requirements
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/GetMessage.java