src/vs/workbench/contrib/notebook/browser/viewModel/notebookViewModelImpl.ts/NotebookViewModel/getNextVisibleCellIndex
class NotebookViewModel:	getNextVisibleCellIndex(index: number) {
		for (let i = 0; i < this._hiddenRanges.length; i++) {
			const cellRange = this._hiddenRanges[i];
			const foldStart = cellRange.start - 1;
			const foldEnd = cellRange.end;

			if (foldEnd < index) {
				continue;
			}

			// foldEnd >= index
			if (foldStart <= index) {
				return foldEnd + 1;
			}

			break;
		}

		return index + 1;
	}