for key, value in project_config.items():
        metadata[key] = value
    # Get custom build config for the current package
    build_config: Dict[str, Any] = (
        config.get("tool", {}).get("pdm", {}).get("build", {})
    )
    # Override PDM build config with custom build config for this package
    for key, value in build_config.items():
        context.config.build_config[key] = value

<div class="termy">

```console
$ pip install "hypercorn[trio]"
---> 100%
```

</div>

### Run with Trio

Then you can pass the command line option `--worker-class` with the value `trio`:

<div class="termy">

```console
$ hypercorn main:app --worker-class trio
```

</div>

And that will start Hypercorn with your app using Trio as the backend.

            "description": "Production environment"
        }
    ],
    "paths": {
            // More stuff here
    }
}
```

!!! tip
    Notice the auto-generated server with a `url` value of `/api/v1`, taken from the `root_path`.

In the docs UI at <a href="http://127.0.0.1:9999/api/v1/docs" class="external-link" target="_blank">http://127.0.0.1:9999/api/v1/docs</a> it would look like:

    x_trace: str = Header(default=..., title="Tracing header"),
):
    return {"message": "Hello World"}
```

...all these parameters are required because the default value is `...` (Ellipsis).

But now it's possible and supported to just omit the default value, as would be done with Pydantic fields, and the parameters would still be required.

✨ For example, this is now supported:

```Python

    If not provided, it's `None` by default, here we provide `"World"` as the default value to use.

Then you could call that Python program:

<div class="termy">

```console
// Here we don't set the env var yet
$ python main.py

// As we didn't set the env var, we get the default value

Hello World from Python

    "joined": "2018-11-30",
}

my_second_user: User = User(**second_user_data)
```

!!! info
    `**second_user_data` means:

    Pass the keys and values of the `second_user_data` dict directly as key-value arguments, equivalent to: `User(id=4, name="Mary", joined="2018-11-30")`

### Editor support