src/vs/workbench/contrib/notebook/common/notebookCommon.ts/parse
	export function parse(cell: URI): { notebook: URI; handle: number } | undefined {
		if (cell.scheme !== scheme) {
			return undefined;
		}

		const idx = cell.fragment.indexOf('s');
		if (idx < 0) {
			return undefined;
		}

		const handle = parseInt(cell.fragment.substring(0, idx).replace(_padRegexp, ''), _radix);
		const _scheme = decodeBase64(cell.fragment.substring(idx + 1)).toString();

		if (isNaN(handle)) {
			return undefined;
		}
		return {
			handle,
			notebook: cell.with({ scheme: _scheme, fragment: null })
		};
	}