# Invalid all cache `cache_all_predecessors` and `cache_all_successors`
	private fun invalidated_all_cache
	do
		if not cache_all_successors.is_empty then cache_all_successors = new HashMap[V, Set[V]]
		if not cache_all_predecessors.is_empty then cache_all_predecessors = new HashMap[V, Set[V]]
	end