extensions/markdown-language-features/src/logger.ts/Logger/data2String
class Logger:	private static data2String(data: any): string {
		if (data instanceof Error) {
			if (isString(data.stack)) {
				return data.stack;
			}
			return (data as Error).message;
		}
		if (isString(data)) {
			return data;
		}
		return JSON.stringify(data, undefined, 2);
	}