src/vs/workbench/api/common/extHostNotebook.ts/ExtHostNotebookController/$openNotebook
class ExtHostNotebookController:	async $openNotebook(viewType: string, uri: UriComponents, backupId: string | undefined, untitledDocumentData: VSBuffer | undefined, token: CancellationToken): Promise<SerializableObjectWithBuffers<NotebookDataDto>> {
		const { provider } = this._getProviderData(viewType);
		const data = await provider.openNotebook(URI.revive(uri), { backupId, untitledDocumentData: untitledDocumentData?.buffer }, token);
		return new SerializableObjectWithBuffers({
			metadata: data.metadata ?? Object.create(null),
			cells: data.cells.map(typeConverters.NotebookCellData.from),
		});
	}