src/vs/platform/instantiation/common/graph.ts/Graph/findCycleSlow
class Graph:	findCycleSlow() {
		for (const [id, node] of this._nodes) {
			const seen = new Set<string>([id]);
			const res = this._findCycle(node, seen);
			if (res) {
				return res;
			}
		}
		return undefined;
	}