function getPathFinder(graph) {
  return path.aStar(graph, {
    distance(fromNode, toNode, link) {
      return link.data.distance;
    },
  });
}
Given a street network (graph), return a pathfinder that can operate on it.
Useful if you modify the street graph during the simulation.

@param {object} graph - An ngraph graph representing an OSM street network.
@returns {object} - An A* pathfinder for the graph.