src/vs/workbench/contrib/notebook/common/notebookEditorModel.ts/ComplexNotebookEditorModel/backup
class ComplexNotebookEditorModel:	async backup(token: CancellationToken): Promise<IWorkingCopyBackup> {

		if (!this.isResolved()) {
			return {};
		}

		const backup = await this._contentProvider.backup(this.resource, token);
		if (token.isCancellationRequested) {
			return {};
		}
		const stats = await this._resolveStats(this.resource);

		if (backup instanceof VSBuffer) {
			return {
				content: bufferToReadable(backup)
			};
		} else {
			return {
				meta: {
					mtime: stats?.mtime ?? Date.now(),
					viewType: this.notebook.viewType,
					backupId: backup
				}
			};
		}

	}