getAllInitialChunks() {
		const chunks = new Set();
		const queue = new Set(this.groupsIterable);
		for (const group of queue) {
			if (group.isInitial()) {
				for (const c of group.chunks) chunks.add(c);
				for (const g of group.childrenIterable) queue.add(g);
			}
		}
		return chunks;
	}
@returns {Set<Chunk>} a set of all the initial chunks (including itself)