src/vs/workbench/contrib/notebook/common/notebookEditorModel.ts/ComplexNotebookEditorModel/notebook
class ComplexNotebookEditorModel:	get notebook(): NotebookTextModel | undefined {
		const candidate = this._notebookService.getNotebookTextModel(this.resource);
		return candidate && candidate.viewType === this.viewType ? candidate : undefined;
	}