assert response.json() == IsDict(
        {
            "detail": [
                {
                    "type": "int_parsing",
                    "loc": ["body", "size"],
                    "msg": "Input should be a valid integer, unable to parse string as an integer",
                    "input": "XL",
                }
            ],
            "body": {"title": "towel", "size": "XL"},
        }
    ) | IsDict(

```Python hl_lines="2  6-8"
{!../../../docs_src/advanced_middleware/tutorial002.py!}
```

The following arguments are supported:

* `allowed_hosts` - A list of domain names that should be allowed as hostnames. Wildcard domains such as `*.example.com` are supported for matching subdomains. To allow any hostname either use `allowed_hosts=["*"]` or omit the middleware.

        {
            "detail": [
                {
                    "type": "string_pattern_mismatch",
                    "loc": ["query", "item-query"],
                    "msg": "String should match pattern '^fixedquery$'",
                    "input": "nonregexquery",
                    "ctx": {"pattern": "^fixedquery$"},
                }
            ]
        }
    ) | IsDict(

For example, you could want to **return a dictionary** or a database object, but **declare it as a Pydantic model**. This way the Pydantic model would do all the data documentation, validation, etc. for the object that you returned (e.g. a dictionary or database object).

Without a data validation system, you would have to do all the checks by hand, in code.

These features are what Marshmallow was built to provide. It is a great library, and I have used it a lot before.

But it was created before there existed Python type hints. So, to define every <abbr title="the definition of how data should be formed">schema</abbr> you need to use specific utils and classes provided by Marshmallow.

    ), "syntaxHighlight should be included and converted to JSON"
    assert (
        '"dom_id": "#swagger-ui"' in response.text
    ), "default configs should be preserved"
    assert "presets: [" in response.text, "default configs should be preserved"
    assert (
        "SwaggerUIBundle.presets.apis," in response.text
    ), "default configs should be preserved"
    assert (

It is provided directly by Starlette, but you can import it from `fastapi`:

```python
from fastapi import WebSocket
```

!!! tip
    When you want to define dependencies that should be compatible with both HTTP and WebSockets, you can define a parameter that takes an `HTTPConnection` instead of a `Request` or a `WebSocket`.

::: fastapi.WebSocket
    options:
        members:
            - scope

client = TestClient(app)


def test_dependency_contextvars():
    """
    Check that custom middlewares don't affect the contextvar context for dependencies.

    The code before yield and the code after yield should be run in the same contextvar
    context, so that request_state_context_var.reset(contextvar_token).

    If they are run in a different context, that raises an error.
    """
    response = client.get("/user")

🍵 💽 🔬 ⚙️, 👆 🔜 ✔️ 🌐 ✅ ✋, 📟.

👫 ⚒ ⚫️❔ 🍭 🏗 🚚. ⚫️ 👑 🗃, & 👤 ✔️ ⚙️ ⚫️ 📚 ⏭.

✋️ ⚫️ ✍ ⏭ 📤 🔀 🐍 🆎 🔑. , 🔬 🔠 <abbr title="the definition of how data should be formed">🔗</abbr> 👆 💪 ⚙️ 🎯 🇨🇻 &amp; 🎓 🚚 🍭.

!!! check "😮 **FastAPI** "
    ⚙️ 📟 🔬 "🔗" 👈 🚚 💽 🆎 &amp; 🔬, 🔁.

# General - How To - Recipes

Here are several pointers to other places in the docs, for general or frequent questions.

## Filter Data - Security

To ensure that you don't return more data than you should, read the docs for [Tutorial - Response Model - Return Type](../tutorial/response-model.md){.internal-link target=_blank}.

## Documentation Tags - OpenAPI