code: def timeit_block(unit='s', label=""):
      
      start = time.time()
      try:
          yield
      finally:
          _format(unit, time.time() - start, label)
docs: 测试代码块耗时
  
      :param unit: 时间单位，有 's','m','h' 可选（seconds，minutes，hours）
      :param label: 代码块标签