code: func newNodeDB(path string, version int, self NodeID) (*nodeDB, error) {
  	if path == "" {
  		return newMemoryNodeDB(self)
  	}
  	return newPersistentNodeDB(path, version, self)
  }
docs: // newNodeDB creates a new node database for storing and retrieving infos about
  // known peers in the network. If no path is given, an in-memory, temporary
  // database is constructed.