code: func NewMVCCLevelDB(path string) (*MVCCLevelDB, error) {
  	var (
  		d   *leveldb.DB
  		err error
  	)
  	if path == "" {
  		d, err = leveldb.Open(storage.NewMemStorage(), nil)
  	} else {
  		d, err = leveldb.OpenFile(path, &opt.Options{BlockCacheCapacity: 600 * 1024 * 1024})
  	}
  
  	return &MVCCLevelDB{db: d}, errors.Trace(err)
  }
docs: // NewMVCCLevelDB returns a new MVCCLevelDB object.