src/vs/base/common/uri.ts/URI/isUri
class URI:	static isUri(thing: any): thing is URI {
		if (thing instanceof URI) {
			return true;
		}
		if (!thing) {
			return false;
		}
		return typeof (<URI>thing).authority === 'string'
			&& typeof (<URI>thing).fragment === 'string'
			&& typeof (<URI>thing).path === 'string'
			&& typeof (<URI>thing).query === 'string'
			&& typeof (<URI>thing).scheme === 'string'
			&& typeof (<URI>thing).fsPath === 'string'
			&& typeof (<URI>thing).with === 'function'
			&& typeof (<URI>thing).toString === 'function';
	}