code: func (mvcc *MVCCLevelDB) Cleanup(key []byte, startTS uint64) error {
  	mvcc.mu.Lock()
  	defer mvcc.mu.Unlock()
  
  	batch := &leveldb.Batch{}
  	err := rollbackKey(mvcc.db, batch, key, startTS)
  	if err != nil {
  		return errors.Trace(err)
  	}
  	return mvcc.db.Write(batch, nil)
  }
docs: // Cleanup implements the MVCCStore interface.