### Based on open standards { #based-on-open-standards }

* <a href="https://github.com/OAI/OpenAPI-Specification" class="external-link" target="_blank"><strong>OpenAPI</strong></a> for API creation, including declarations of <abbr title="also known as: endpoints, routes">path</abbr> <abbr title="also known as HTTP methods, as POST, GET, PUT, DELETE">operations</abbr>, parameters, request bodies, security, etc.

But you can re-order them, and have the value without a default (the query parameter `q`) first.

It doesn't matter for **FastAPI**. It will detect the parameters by their names, types and default declarations (`Query`, `Path`, etc), it doesn't care about the order.

So, you can declare your function as:

//// tab | Python 3.8 non-Annotated

/// tip

Prefer to use the `Annotated` version if possible.

///

///

## Duplicate headers { #duplicate-headers }

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:

///

### <a href="https://github.com/hugapi/hug" class="external-link" target="_blank">Hug</a>

    return accessibleObject.getDeclaredAnnotations();
  }

  // We ought to be able to implement GenericDeclaration instead its parent AnnotatedElement.
  // That would give us this method declaration. But for some reason, implementing
  // GenericDeclaration leads to weird errors in Android tests:
  // IncompatibleClassChangeError: interface not implemented

  }

  @GwtIncompatible
  @J2ktIncompatible
  /*
   * The mainline copy of ImmutableMapValues doesn't produce this serialized form anymore, though
   * the backport does. For now, we're keeping the class declaration in *both* flavors so that both
   * flavors can read old data or data from the other flavor. However, we strongly discourage
   * relying on this, as we have made incompatible changes to serialized forms in the past and

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nonnull;
import org.apache.maven.api.annotations.Nullable;

/**
 * Parses and evaluates version ranges encountered in dependency declarations.
 *
 * @since 4.0.0
 */
@Experimental
@Consumer
public interface VersionRangeResolver extends Service {

    /**
     * Expands a version range to a list of matching versions, in ascending order.

**FastAPI** te oferece o seguinte:

### Baseado em padrões abertos

* <a href="https://github.com/OAI/OpenAPI-Specification" class="external-link" target="_blank"><strong>OpenAPI</strong></a> para criação de APIs, incluindo declarações de <abbr title="também conhecido como métodos HTTP, como POST, GET, PUT, DELETE">operações</abbr> de <abbr title="também conhecido como: endpoints, routes">caminho</abbr>, parâmetros, requisições de corpo, segurança etc.

To create the callback *path operation* use the same `APIRouter` you created above.

It should look just like a normal FastAPI *path operation*:

* It should probably have a declaration of the body it should receive, e.g. `body: InvoiceEvent`.
* And it could also have a declaration of the response it should return, e.g. `response_model=InvoiceEventReceived`.

{* ../../docs_src/openapi_callbacks/tutorial001.py hl[16:18,21:22,28:32] *}

This actually inspired updating parts of Pydantic, to support the same validation declaration style (all this functionality is now already available in Pydantic).

///

### <a href="https://github.com/hugapi/hug" class="external-link" target="_blank">Hug</a> { #hug }