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 match = _regex.exec(cell.fragment);
		if (!match) {
			return undefined;
		}
		const handle = Number(match[1]);
		return {
			handle,
			notebook: cell.with({
				scheme: cell.fragment.substr(match[0].length) || Schemas.file,
				fragment: null
			})
		};
	}