code: def argmin_random_tie(seq, fn):
      
      best_score = fn(seq[0]); n = 0
      for x in seq:
          x_score = fn(x)
          if x_score < best_score:
              best, best_score = x, x_score; n = 1
          elif x_score == best_score:
              n += 1
              if random.randrange(n) == 0:
                  best = x
      return best
docs: Return an element with lowest fn(seq[i]) score; break ties at random.
      Thus, for all s,f: argmin_random_tie(s, f) in argmin_list(s, f)