///

## Declare model attributes

You can then use `Field` with model attributes:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[11:14] *}

`Field` works the same way as `Query`, `Path` and `Body`, it has all the same parameters, etc.

/// note | "Technical Details"

The parameter `name` is defined as `Optional[str]`, but it is **not optional**, you cannot call the function without the parameter:

```Python
say_hi()  # Oh, no, this throws an error! 😱
```

The `name` parameter is **still required** (not *optional*) because it doesn't have a default value. Still, `name` accepts `None` as the value:

```Python
say_hi(name=None)  # This works, None is valid 🎉
```

### Same Schema for Input and Output Models in Docs

And now there will be one single schema for input and output for the model, only `Item`, and it will have `description` as **not required**:

<div class="screenshot">
<img src="/img/tutorial/separate-openapi-schemas/image05.png">
</div>

#### Fix it with `secrets.compare_digest()`

But in our code we are actually using `secrets.compare_digest()`.

In short, it will take the same time to compare `stanleyjobsox` to `stanleyjobson` than it takes to compare `johndoe` to `stanleyjobson`. And the same for the password.

That way, using `secrets.compare_digest()` in your application code, it will be safe against this whole range of security attacks.

After that, all of the processing logic is the same.

But because of our changes in `GzipRequest.body`, the request body will be automatically decompressed when it is loaded by **FastAPI** when needed.

## Accessing the request body in an exception handler

/// tip

And of course, it supports the same:

* data validation
* data serialization
* data documentation, etc.

This works the same way as with Pydantic models. And it is actually achieved in the same way underneath, using Pydantic.

/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

This is the same mechanism used when you give permissions while logging in with Facebook, Google, GitHub, etc:

<img src="/img/tutorial/security/image11.png">

## JWT token with scopes

Now, modify the token *path operation* to return the scopes requested.

This will be especially useful when you use it in a **large code base** where you use **the same dependencies** over and over again in **many *path operations***.

## To `async` or not to `async`

As dependencies will also be called by **FastAPI** (the same as your *path operation functions*), the same rules apply while defining your functions.

/// info

The parameter `summary` is available in OpenAPI 3.1.0 and above, supported by FastAPI 0.99.0 and above.

///

## Overriding the defaults

Using the information above, you can use the same utility function to generate the OpenAPI schema and override each part that you need.

                    }
                }
            }
        }
    }
}
```

## Additional media types for the main response

You can use this same `responses` parameter to add different media types for the same main response.

For example, you can add an additional media type of `image/png`, declaring that your *path operation* can return a JSON object (with media type `application/json`) or a PNG image: