src/vs/workbench/api/common/extHostNotebook.ts/ExtHostNotebookController/$notebookToData
class ExtHostNotebookController:	async $notebookToData(handle: number, data: SerializableObjectWithBuffers<NotebookDataDto>, token: CancellationToken): Promise<VSBuffer> {
		const serializer = this._notebookSerializer.get(handle);
		if (!serializer) {
			throw new Error('NO serializer found');
		}
		const bytes = await serializer.serializeNotebook(typeConverters.NotebookData.to(data.value), token);
		return VSBuffer.wrap(bytes);
	}