It is possible to receive duplicate headers. That means, the same header with multiple values.

You can define those cases using a list in the type declaration.

You will receive all the values from the duplicate header as a Python `list`.

For example, to declare a header of `X-Token` that can appear more than once, you can write:

{* ../../docs_src/header_params/tutorial003_an_py310.py hl[9] *}

    # o filterVariablesMap: (NotRequired - Default map:{})
    #  You can specify the filter variables for DDL.
    #
    #; filterVariablesMap = map:{abc=AAA}
    # - - - - - - - - - -/

    # /- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    # o additionalUserMap: (NotRequired - Default map:{})
    #  You can set additional users.
    #  Elements of this map are as below:

There are several parameters that you can pass to your *path operation decorator* to configure it.

/// warning

Notice that these parameters are passed directly to the *path operation decorator*, not to your *path operation function*.

///

## Response Status Code { #response-status-code }

You can define the (HTTP) `status_code` to be used in the response of your *path operation*.

You can pass directly the `int` code, like `404`.

::: fastapi.middleware.cors.CORSMiddleware

It can be imported from `fastapi`:

```python
from fastapi.middleware.cors import CORSMiddleware
```

::: fastapi.middleware.gzip.GZipMiddleware

It can be imported from `fastapi`:

```python
from fastapi.middleware.gzip import GZipMiddleware
```

::: fastapi.middleware.httpsredirect.HTTPSRedirectMiddleware

It can be imported from `fastapi`:

```python

     * OS family that can be tested for. {@value}
     */
    private static final String FAMILY_OS2 = "os/2";

    /**
     * OS family that can be tested for. {@value}
     */
    private static final String FAMILY_NETWARE = "netware";

    /**
     * OS family that can be tested for. {@value}
     */
    private static final String FAMILY_DOS = "dos";

    /**
     * OS family that can be tested for. {@value}
     */

}
```

## Additional media types for the main response { #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:

But this way we can focus on how the **Dependency Injection** system works.

### Create a dependency, or "dependable" { #create-a-dependency-or-dependable }

Let's first focus on the dependency.

It is just a function that can take all the same parameters that a *path operation function* can take:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

# Response Model - Return Type { #response-model-return-type }

You can declare the type used for the response by annotating the *path operation function* **return type**.

You can use **type annotations** the same way you would for input data in function **parameters**, you can use Pydantic models, lists, dictionaries, scalar values like integers, booleans, etc.

{* ../../docs_src/response_model/tutorial001_01_py310.py hl[16,21] *}

## Nested Models { #nested-models }

Each attribute of a Pydantic model has a type.

But that type can itself be another Pydantic model.

So, you can declare deeply nested JSON "objects" with specific attribute names, types and validations.

All that, arbitrarily nested.

### Define a submodel { #define-a-submodel }

For example, we can define an `Image` model:

{* ../../docs_src/body_nested_models/tutorial004_py310.py hl[7:9] *}

# Path Parameters and Numeric Validations { #path-parameters-and-numeric-validations }

In the same way that you can declare more validations and metadata for query parameters with `Query`, you can declare the same type of validations and metadata for path parameters with `Path`.

## Import `Path` { #import-path }

First, import `Path` from `fastapi`, and import `Annotated`:

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[1,3] *}