src/vs/workbench/contrib/notebook/browser/diff/diffElementViewModel.ts/getStreamOutputData
export function getStreamOutputData(outputs: IOutputItemDto[]) {
	if (!outputs.length) {
		return null;
	}

	const first = outputs[0];
	const mime = first.mime;
	const sameStream = !outputs.find(op => op.mime !== mime);

	if (sameStream) {
		return outputs.map(opit => opit.data.toString()).join('');
	} else {
		return null;
	}
}