@Override
  public String toString() {
    StringBuilder result = new StringBuilder();
    result.append("seqNo").append(lastSequenceNumber);
    if (versionTag != null) {
      result.append(",").append(versionTag);
    }
    return result.toString();
  }
version tag, if any, for the operation
geode-core/src/main/java/org/apache/geode/internal/cache/event/EventSequenceNumberHolder.java