// The remaining payload and versions are returned.
func checkXL2V1(buf []byte) (payload []byte, major, minor uint16, e error) {
	if len(buf) <= 8 {
		return payload, 0, 0, fmt.Errorf("xlMeta: no data")
	}

	if !bytes.Equal(buf[:4], xlHeader[:]) {
		return payload, 0, 0, fmt.Errorf("xlMeta: unknown XLv2 header, expected %v, got %v", xlHeader[:4], buf[:4])
	}

```

</div>

<details markdown="1">
<summary>নির্দেশনা সম্পর্কে <code>uvicorn main:app --reload</code>...</summary>

`uvicorn main:app` নির্দেশনাটি দ্বারা বোঝায়:

- `main`: ফাইল `main.py` (পাইথন "মডিউল")।
- `app`: `app = FastAPI()` লাইন দিয়ে `main.py` এর ভিতরে তৈরি করা অবজেক্ট।
- `--reload`: কোড পরিবর্তনের পরে সার্ভার পুনরায় চালু করুন। এটি শুধুমাত্র ডেভেলপমেন্ট এর সময় ব্যবহার করুন।

</details>

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

INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [28720]
INFO:     Started server process [28722]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
```

</div>

<details markdown="1">
<summary>A parancsról <code>uvicorn main:app --reload</code>...</summary>

		// Test case with "X-Amz-Content-Sha256" not set so we can skip.
		{"", "", "", "", true},

		// Test case - 3.
		// Test case with "X-Amz-Content-Sha256" header set to  "UNSIGNED-PAYLOAD"
		// When "X-Amz-Content-Sha256" header is set to  "UNSIGNED-PAYLOAD", validation of content sha256 has to be skipped.
		{"X-Amz-Content-Sha256", unsignedPayload, "X-Amz-Credential", "", true},

		// Test case - 4.

        if (isRetainPayload()) {
            final byte[] payload = new byte[len];
            System.arraycopy(buffer, start, payload, 0, len);
            setRawPayload(payload);
        }

        if (!verifySignature(buffer, start, len)) {

Let's start with a simple FastAPI application:

{* ../../docs_src/generate_clients/tutorial001_py39.py hl[7:9,12:13,16:17,21] *}

Notice that the *path operations* define the models they use for request payload and response payload, using the models `Item` and `ResponseMessage`.

### API Docs { #api-docs }

If you go to `/docs`, you will see that it has the **schemas** for the data to be sent in requests and received in responses:

```

</div>

<details markdown="1">
<summary>Informazioni sul comando <code>uvicorn main:app --reload</code>...</summary>

Vediamo il comando `uvicorn main:app` in dettaglio:

* `main`: il file `main.py` (il "modulo" Python).
* `app`: l'oggetto creato dentro `main.py` con la riga di codice `app = FastAPI()`.
* `--reload`: ricarica il server se vengono rilevati cambiamenti del codice. Usalo solo durante la fase di sviluppo.

```

</div>

<details markdown="1">
<summary>Was macht der Befehl <code>uvicorn main:app --reload</code> ...</summary>

Der Befehl `uvicorn main:app` bezieht sich auf:

* `main`: die Datei `main.py` (das Python-„Modul“).
* `app`: das Objekt, das innerhalb von `main.py` mit der Zeile `app = FastAPI()` erzeugt wurde.
* `--reload`: lässt den Server nach Codeänderungen neu starten. Tun Sie das nur während der Entwicklung.

</details>

👆 💪 👟 🔙 & 👀 ⚫️❔ ⚫️❔ 👆 💪.

## 🏃 📟

🌐 📟 🍫 💪 📁 & ⚙️ 🔗 (👫 🤙 💯 🐍 📁).

🏃 🙆 🖼, 📁 📟 📁 `main.py`, & ▶️ `uvicorn` ⏮️:

<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]

### Test it { #test-it }

Now, you should be able to go to your docs at <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>, and reload the page, it will load those assets from the new CDN.

## Self-hosting JavaScript and CSS for docs { #self-hosting-javascript-and-css-for-docs }