src/vs/workbench/contrib/notebook/browser/notebookEditorServiceImpl.ts/NotebookEditorWidgetService/addNotebookEditor
class NotebookEditorWidgetService:	addNotebookEditor(editor: INotebookEditor): void {
		this._notebookEditors.set(editor.getId(), editor);
		this._onNotebookEditorAdd.fire(editor);
	}