src/vs/editor/contrib/stickyScroll/browser/stickyScrollProvider.ts/StickyOutlineElement/findSumOfRangesOfGroup
class StickyOutlineElement:	private static findSumOfRangesOfGroup(outline: OutlineGroup | OutlineElement): number {
		let res = 0;
		for (const child of outline.children.values()) {
			res += this.findSumOfRangesOfGroup(child);
		}
		if (outline instanceof OutlineElement) {
			return res + outline.symbol.range.endLineNumber - outline.symbol.selectionRange.startLineNumber;
		} else {
			return res;
		}
	}