code: func (db *Database) Nodes() []common.Hash {
  	db.lock.RLock()
  	defer db.lock.RUnlock()
  
  	var hashes = make([]common.Hash, 0, len(db.dirties))
  	for hash := range db.dirties {
  		if hash != (common.Hash{}) { // Special case for "root" references/nodes
  			hashes = append(hashes, hash)
  		}
  	}
  	return hashes
  }
docs: // Nodes retrieves the hashes of all the nodes cached within the memory database.
  // This method is extremely expensive and should only be used to validate internal
  // states in test code.