message: viewer clear in benchmark runner
diff: @@ -170,7 +170,7 @@ class BenchmarkRunner:
  viewer.drawWorld(world, scenario._eval_agent_ids, benchmark_config.scenario_idx)
  viewer.show(block=False)
  time.sleep(step_time)
  -
  + viewer.clear()
  try:
  world.Step(step_time)
  except Exception as e:
  