The Traveling Salesman Problem (TSP) is a classic optimization challenge that seeks the shortest possible route for a salesman to visit each city in a list exactly once and return to the origin city. 
We will use Ant Colony Optimization (ACO) algorithm to solve this problem. 
Your task is to find a `heuristic` function for the ACO algorithm. This function will generate the heuristic matrix for the ACO algorithm.
Your goal is to minimize the objective, which is the average test tour distances for the salesman (called "score" or "objective" of solution).