src/vs/editor/common/model/bracketPairsTextModelPart/bracketPairsTree/smallImmutableSet.ts/DenseKeyProvider/reverseLookupSet
class DenseKeyProvider:	reverseLookupSet(set: SmallImmutableSet<T>): T[] {
		const result: T[] = [];
		for (const [key] of this.items) {
			if (set.has(key, this)) {
				result.push(key);
			}
		}
		return result;
	}