struct find_approximate_number_of_cliques_visitor
    {
        typedef typename boost::graph_traits<BaseGraph>::vertex_descriptor Vertex;
        typedef typename boost::graph_traits<BaseGraph>::vertex_iterator VertexIterator;
        typedef std::deque<Vertex> Clique;

        // What size cliques we are looking for.
        int desired_clique_size;
        // Total number of cliques of size desired_clique_size (INCLUDING OVERLAPPING CLIQUES)
        long long total_number_of_cliques;

        // Constructor
        find_approximate_number_of_cliques_visitor(int size) : desired_clique_size(size), total_number_of_cliques(0) {}

        // Called when a maximal clique is found
        template <typename Clique, typename BaseGraph>
        void clique(const Clique& maximal_clique, const BaseGraph& g)
        {
            std::cout << "in clique start (approx), size:" << maximal_clique.size() << ", total number:" << total_number_of_cliques << std::endl;
            // TODO: may need to sort edges?
            int maxclique_size = maximal_clique.size();
            std::cout << "in clique (approx), size:" << maximal_clique.size() << std::endl;
            long long number_of_cliques = 0;
            if(maxclique_size < desired_clique_size)
                number_of_cliques = 0;
            else
                number_of_cliques = 1;
            std::cout << "in clique preloop(approx), number_of_cliques:" << number_of_cliques << std::endl;
            // Repeat maxclique_size - desired_clique_size times.
            for(int i = maxclique_size; i > desired_clique_size; --i) {
                std::cout << "in clique loop(approx), number_of_cliques:" << number_of_cliques << ", i:" << i << std::endl;
                number_of_cliques *= i;
            }
            std::cout << "in clique postloop(approx), number_of_cliques:" << number_of_cliques << std::endl;
            total_number_of_cliques += number_of_cliques;
            std::cout << "in clique end(approx), total_number_of_cliques:" << total_number_of_cliques << std::endl;
        }
    };