code: func newMemoryDB() (*DB, error) {
  	db, err := leveldb.Open(storage.NewMemStorage(), nil)
  	if err != nil {
  		return nil, err
  	}
  	return &DB{lvl: db, quit: make(chan struct{})}, nil
  }
docs: // newMemoryNodeDB creates a new in-memory node database without a persistent backend.