* Fix callback handling for sub-routers. PR [#792](https://github.com/tiangolo/fastapi/pull/792) by [@jekirl](https://github.com/jekirl).
* Fix typos. PR [#784](https://github.com/tiangolo/fastapi/pull/784) by [@kkinder](https://github.com/kkinder).
* Add 4 Japanese articles to [External Links](https://fastapi.tiangolo.com/external-links/). PR [#783](https://github.com/tiangolo/fastapi/pull/783) by [@HymanZHAN](https://github.com/HymanZHAN).

    fun start()
  }

  private object TestThreadSerialTask : SerialTask {
    override fun start() = error("unexpected call")
  }

  inner class RunnableSerialTask(
    private val runnable: Runnable,
  ) : SerialTask {
    override fun start() {
      taskRunner.assertThreadHoldsLock()
      require(currentTask == this)
      activeThreads++

        `element_spec` argument of `tf.data.experimental.load` when loading the
        previously saved dataset.
    *   Add `.element_spec` property to `tf.data.DatasetSpec` to access the
        inner spec. This can be used to extract the structure of nested
        datasets.
    *   Add `tf.data.experimental.AutoShardingPolicy.HINT` which can be used to