src/vs/workbench/contrib/audioCues/browser/audioCueLineFeatureContribution.ts/FoldedAreaLineFeature/getObservableState
class FoldedAreaLineFeature:	getObservableState(editor: ICodeEditor, model: ITextModel): IObservable<LineFeatureState> {
		const foldingController = FoldingController.get(editor);
		if (!foldingController) {
			return constObservable({
				isPresent: () => false,
			});
		}

		const foldingModel = observableFromPromise(
			foldingController.getFoldingModel() ?? Promise.resolve(undefined)
		);
		return foldingModel.map<LineFeatureState>((v) => ({
			isPresent: (lineNumber) => {
				const regionAtLine = v.value?.getRegionAtLine(lineNumber);
				const hasFolding = !regionAtLine
					? false
					: regionAtLine.isCollapsed &&
					regionAtLine.startLineNumber === lineNumber;
				return hasFolding;
			},
		}));
	}