docs: def rand_block(minimum, scale, maximum=1):
      """
          block current thread at random pareto time ``minimum < block < 15`` and return the sleep time ``seconds``
  
      :param minimum:
      :type minimum:
      :param scale:
      :type scale:
      :param slow_mode: a tuple e.g.(2, 5)
      :type slow_mode: tuple
      :return:
      """
      t = min(rand_pareto_float(minimum, scale), maximum)
      time.sleep(t)
      return t