src/vs/editor/contrib/folding/foldingModel.ts/FoldingModel/getAllRegionsAtLine
class FoldingModel:	getAllRegionsAtLine(lineNumber: number, filter?: (r: FoldingRegion, level: number) => boolean): FoldingRegion[] {
		let result: FoldingRegion[] = [];
		if (this._regions) {
			let index = this._regions.findRange(lineNumber);
			let level = 1;
			while (index >= 0) {
				let current = this._regions.toRegion(index);
				if (!filter || filter(current, level)) {
					result.push(current);
				}
				level++;
				index = current.parentIndex;
			}
		}
		return result;
	}