@Override
  protected void appendFields(StringBuilder buff) {
    super.appendFields(buff);
    buff.append("; keys=").append(keys.size());
    buff.append("; eventID=").append(eventID);
  }
Empty constructor to satisfy {@link DataSerializer} requirements
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/PRTombstoneMessage.java