}

  companion object {
    @JvmOverloads
    fun body(
      hex: String,
      charset: String? = null,
    ): ResponseBody {
      val mediaType = if (charset == null) null else "any/thing; charset=$charset".toMediaType()
      return hex.decodeHex().toResponseBody(mediaType)
    }

    fun exhaust(reader: Reader): String {
      val builder = StringBuilder()
      val buf = CharArray(10)

016D          ; valid                                  # 1.1  LATIN SMALL LETTER U WITH BREVE
016E          ; mapped                 ; 016F          # 1.1  LATIN CAPITAL LETTER U WITH RING ABOVE
016F          ; valid                                  # 1.1  LATIN SMALL LETTER U WITH RING ABOVE
0170          ; mapped                 ; 0171          # 1.1  LATIN CAPITAL LETTER U WITH DOUBLE ACUTE

  private final long totalLoadTime;

  private final long evictionCount;

  /**
   * Constructs a new {@code CacheStats} instance.
   *
   * <p>Five parameters of the same type in a row is a bad thing, but this class is not constructed
   * by end users and is too fine-grained for a builder.
   */
  @SuppressWarnings("GoodTime") // should accept a java.time.Duration
  public CacheStats(
      long hitCount,

Trong nhiều trường hợp, cách các biến môi trường trở nên hữu ích và có thể áp dụng không thực sự rõ ràng ngay từ đầu, nhưng chúng sẽ liên tục xuất hiện trong rất nhiều tình huống khi bạn phát triển ứng dụng, vì vậy việc hiểu biết về chúng là hữu ích.

```Python
q: Annotated[str | None] = None
```

////

//// tab | Python 3.8+

```Python
q: Annotated[Union[str, None]] = None
```

////

Both of those versions mean the same thing, `q` is a parameter that can be a `str` or `None`, and by default, it is `None`.

Now let's jump to the fun stuff. 🎉

## Add `Query` to `Annotated` in the `q` parameter { #add-query-to-annotated-in-the-q-parameter }

     * crc2 = int2
     * crc3 = int3
     *
     * ...so we set crc0 so that computeForWord(crc0) = -1 and xoring it with the first int
     * gives us the desired result.  computeForWord(0) == 0, so all the others do the right thing.
     */
    private int crc0 = INVERSE_COMPUTE_FOR_WORD_OF_ALL_1S;
    private int crc1 = 0;
    private int crc2 = 0;
    private int crc3 = 0;

    @Override
    protected void process(ByteBuffer bb) {

In contrast to a "**container image**" that is the stored static contents, a "**container**" normally refers to the running instance, the thing that is being **executed**.

/// tip

The `callback_url` query parameter uses a Pydantic <a href="https://docs.pydantic.dev/latest/api/networks/" class="external-link" target="_blank">Url</a> type.

///

The only new thing is the `callbacks=invoices_callback_router.routes` as an argument to the *path operation decorator*. We'll see what that is next.

## Documenting the callback { #documenting-the-callback }

# Những bước đầu tiên

Tệp tin FastAPI đơn giản nhất có thể trông như này:

{* ../../docs_src/first_steps/tutorial001.py *}

Sao chép sang một tệp tin `main.py`.

Chạy live server:

<div class="termy">

```console
$ uvicorn main:app --reload

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
<span style="color: green;">INFO</span>:     Started reloader process [28720]

   * list to {@link com.google.common.collect.ImmutableList#copyOf(Collection) ImmutableList.copyOf}
   * and use that list instead.
   */
  public List<Long> asList() {
    /*
     * Typically we cache this kind of thing, but much repeated use of this view is a performance
     * anti-pattern anyway. If we cache, then everyone pays a price in memory footprint even if
     * they never use this method.
     */
    return new AsList(this);