Here is a hint : if V denotes your set of 5 vertices., construct a graph whose vertices is V and for every par of vertices u and v of V, label the edge (u,v) with the length of the shortest path between u and v in the original graph (use the shortest_path method). What you want is a TSP in that reduced graph (use the traveling_salesman_problem method, with the option use_edge_labels=True.