src/vs/editor/common/model/textModel.ts/TextModel/_setTrackedRange
class TextModel:	_setTrackedRange(id: string | null, newRange: Range | null, newStickiness: model.TrackedRangeStickiness): string | null {
		const node = (id ? this._decorations[id] : null);

		if (!node) {
			if (!newRange) {
				// node doesn't exist, the request is to delete => nothing to do
				return null;
			}
			// node doesn't exist, the request is to set => add the tracked range
			return this._deltaDecorationsImpl(0, [], [{ range: newRange, 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;
		}

		// node exists, the request is to set => change the tracked range and its options
		const range = this._validateRangeRelaxedNoAllocations(newRange);
		const startOffset = this._buffer.getOffsetAt(range.startLineNumber, range.startColumn);
		const endOffset = this._buffer.getOffsetAt(range.endLineNumber, range.endColumn);
		this._decorationsTree.delete(node);
		node.reset(this.getVersionId(), startOffset, endOffset, range);
		node.setOptions(TRACKED_RANGE_OPTIONS[newStickiness]);
		this._decorationsTree.insert(node);
		return node.id;
	}