NotesManager | Менеджер заметок

I am making a simple note taking app to learn node and ES6. I have 3 modules - App, NotesManager and Note. I am importing the Note class into the NotesManager and am trying to instantiate it in its addNote function. The problem is that even though the import is correct, it turns out to be undefined inside the class definition. A simpler solution would be to just instantiate the NotesManager class and add the Note class to its constructor however, I want to have NotesManager as a static utility class.

Here is my code. Note.js