This function assumes the 2d distance is meant

def furthest(self, ps: Union["Units", List["Point2"], Set["Point2"]]) -> Union["Unit", "Pointlike"]:
        """ This function assumes the 2d distance is meant """
        assert ps
        if len(ps) == 1:
            return ps[0]
        furthest_distance_squared = -math.inf
        for p2 in ps:
            p2pos = p2
            if not isinstance(p2pos, Point2):
                p2pos = p2.position
            distance = (self[0] - p2pos[0]) ** 2 + (self[1] - p2pos[1]) ** 2
            if furthest_distance_squared < distance:
                furthest_distance_squared = distance
                furthest_element = p2
        return furthest_element