@Override
  public long lastUpdate() {
    return undoLog.isEmpty() ? 0L : undoLog.get(undoLog.size() - 1).level;
  }
Create an UndoMap backed by another Map instance.

@param delegate The Map instance to use for backing storage
evm/src/main/java/org/hyperledger/besu/collections/undo/UndoMap.java