### The callback path expression

### Import typing's `List`

In Python 3.9 and above you can use the standard `list` to declare these type annotations as we'll see below. 💡

But in Python versions before 3.9 (3.6 and above), you first need to import `List` from standard Python's `typing` module:

```Python hl_lines="1"
{!> ../../docs_src/body_nested_models/tutorial002.py!}
```

### A expressão do caminho do callback

---> 100%
```

</div>

⚫️ 🔜 🔍 📁 &amp; 💯 🔁, 🛠️ 👫, &amp; 📄 🏁 🔙 👆.

🏃 💯 ⏮️:

<div class="termy">

```console
$ pytest

================ test session starts ================
platform linux -- Python 3.6.9, pytest-5.3.5, py-1.8.1, pluggy-0.13.1
rootdir: /home/user/code/superawesome-cli/app
plugins: forked-1.1.3, xdist-1.31.0, cov-2.8.1
collected 6 items

---> 100%

	res := map[string]ParentUserInfo{}
	for _, ui := range cache.iamUsersMap {
		cred := ui.Credentials
		// Only consider service account or STS credentials with
		// non-empty session tokens.
		if !(cred.IsServiceAccount() || cred.IsTemp()) ||
			cred.SessionToken == "" {
			continue
		}

		var (
			err    error
			claims *jwt.MapClaims
		)

```console
$ pip install pytest

---> 100%
```

</div>

他会自动检测文件和测试，执行测试，然后向你报告结果。

执行测试：

<div class="termy">

```console
$ pytest

================ test session starts ================
platform linux -- Python 3.6.9, pytest-5.3.5, py-1.8.1, pluggy-0.13.1
rootdir: /home/user/code/superawesome-cli/app
plugins: forked-1.1.3, xdist-1.31.0, cov-2.8.1
collected 6 items

---> 100%

	var uv uuid.UUID
	var err error
	switch fi.VersionID {
	case "", nullVersionID:
	default:
		uv, err = uuid.Parse(fi.VersionID)
		if err != nil {
			return err
		}
	}

	for i, version := range x.versions {
		if version.header.VersionID != uv || version.header.Type != ObjectType {
			continue
		}
		// if uv has tiered content we add a
		// free-version to track it for asynchronous
		// deletion via scanner.

    opt raise
        dep -->> handler: Raise HTTPException
        handler -->> client: HTTP error response
        dep -->> dep: Raise other exception
    end
    dep ->> operation: Run dependency, e.g. DB session
    opt raise
        operation -->> dep: Raise HTTPException
        dep -->> handler: Auto forward exception
        handler -->> client: HTTP error response
        operation -->> dep: Raise other exception

If you have an older version, you would get errors when trying to use `Annotated`.

Make sure you [Upgrade the FastAPI version](../../deployment/versions.md#upgrading-the-fastapi-versions){.internal-link target=_blank} to at least 0.95.1 before using `Annotated`.

///

### Import `Depends`

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[3] *}

    opt raise
        dep -->> handler: Raise HTTPException
        handler -->> client: HTTP error response
        dep -->> dep: Raise other exception
    end
    dep ->> operation: Run dependency, e.g. DB session
    opt raise
        operation -->> handler: Raise HTTPException
        handler -->> client: HTTP error response
        operation -->> dep: Raise other exception
    end