src/vs/workbench/contrib/notebook/browser/viewModel/notebookViewModel.ts/NotebookViewModel/setTrackedRange
class NotebookViewModel:	setTrackedRange(id: string | null, newRange: ICellRange | null, newStickiness: TrackedRangeStickiness): string | null {
		const node = (id ? this._decorations[id] : null);

		if (!node) {
			if (!newRange) {
				return null;
			}

			return this._deltaCellDecorationsImpl(0, [], [{ range: new Range(newRange.start + 1, 1, newRange.end + 1, 1), options: TRACKED_RANGE_OPTIONS[newStickiness] }])[0];
		}

		if (!newRange) {
			// node exists, the request is to delete => delete node
			this._decorationsTree.delete(node);
			delete this._decorations[node.id];
			return null;
		}

		this._decorationsTree.delete(node);
		node.reset(this.getVersionId(), newRange.start, newRange.end + 1, new Range(newRange.start + 1, 1, newRange.end + 1, 1));
		node.setOptions(TRACKED_RANGE_OPTIONS[newStickiness]);
		this._decorationsTree.insert(node);
		return node.id;
	}