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
            - app

    A `Request` also has a `request.receive`, that's a function to "receive" the body of the request.

    The `scope` `dict` and `receive` function are both part of the ASGI specification.

    And those two things, `scope` and `receive`, are what is needed to create a new `Request` instance.

{!../../../docs_src/bigger_applications/app/routers/items.py!}
```

!!! tip
    This last path operation will have the combination of tags: `["items", "custom"]`.

    And it will also have both responses in the documentation, one for `404` and one for `403`.

## The main `FastAPI`

Now, let's see the module at `app/main.py`.

Here's where you import and use the class `FastAPI`.

    {!> ../../../docs_src/python_types/tutorial008b_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="1  4"
    {!> ../../../docs_src/python_types/tutorial008b.py!}
    ```

In both cases this means that `item` could be an `int` or a `str`.

#### Possibly `None`

You can declare that a value could have a type, like `str`, but that it could also be `None`.

This means that you can install the new Pydantic v2, and if something fails, you can install Pydantic v1 while you fix any problems you might have, but having the latest FastAPI.

There are **tests for both Pydantic v1 and v2**, and test **coverage** is kept at **100%**.

### Changes

* There are **new parameter** fields supported by Pydantic `Field()` for:

    * `Path()`
    * `Query()`

    ```

Those parameters are what **FastAPI** will use to "solve" the dependency.

In both cases, it will have:

* An optional `q` query parameter that is a `str`.
* A `skip` query parameter that is an `int`, with a default of `0`.
* A `limit` query parameter that is an `int`, with a default of `100`.

In both cases the data will be converted, validated, documented on the OpenAPI schema, etc.

## Use it

    You can probably skip this part.

There's an alternative way to define this logic to be executed during *startup* and during *shutdown*.

* for **output** it will be **required** (and possibly `None`, or in JSON terms, `null`)

### Model for Output in Docs

You can check the output model in the docs too, **both** `name` and `description` are marked as **required** with a **red asterisk**:

<div class="screenshot">
<img src="/img/tutorial/separate-openapi-schemas/image03.png">
</div>

### Model for Input and Output in Docs

This way, if any part of Starlette's internal code, or a Starlette extension or plug-in, raises a Starlette `HTTPException`, your handler will be able to catch and handle it.

In this example, to be able to have both `HTTPException`s in the same code, Starlette's exceptions is renamed to `StarletteHTTPException`:

```Python
from starlette.exceptions import HTTPException as StarletteHTTPException
```

You will see the JSON response as:

```JSON
{"item_id": 5, "q": "somequery"}
```

You already created an API that:

* Receives HTTP requests in the _paths_ `/` and `/items/{item_id}`.
* Both _paths_ take `GET` operations (also known as HTTP _methods_).
* The _path_ `/items/{item_id}` has a _path parameter_ `item_id` that should be an `int`.