Si tienes un grupo de **parámetros de header** relacionados, puedes crear un **modelo Pydantic** para declararlos.

Esto te permitirá **reutilizar el modelo** en **múltiples lugares** y también declarar validaciones y metadatos para todos los parámetros al mismo tiempo. 😎

/// note | Nota

Esto es compatible desde la versión `0.115.0` de FastAPI. 🤓

///

        assertEquals(1, pairs.size(), "Should start with 1 pair");

        AvPairs.remove(pairs, AvPair.MsvAvFlags);

        assertEquals(1, pairs.size(), "Should still have 1 pair");
        assertTrue(AvPairs.contains(pairs, AvPair.MsvAvTimestamp), "Should still contain MsvAvTimestamp");
    }

    /**
     * Test replace method
     */
    @Test
    @DisplayName("Replace should remove old and add new")

{* ../../docs_src/response_headers/tutorial002_py39.py hl[1, 7:8] *}

And then you can return any object you need, as you normally would (a `dict`, a database model, etc).

And if you declared a `response_model`, it will still be used to filter and convert the object you returned.

    }

    /**
     * Gets the identifier of the POM whose effective model could not be built. The general format of the identifier is
     * {@code <groupId>:<artifactId>:<version>} but some of these coordinates may still be unknown at the point the
     * exception is thrown so this information is merely meant to assist the user.
     *
     * @return The identifier of the POM or an empty string if not known, never {@code null}.
     */

Still, in both situations, chances are that **FastAPI** will [still be faster](index.md#performance){.internal-link target=_blank} than (or at least comparable to) your previous framework.

### Dependencies { #dependencies }

Let's say the file dedicated to handling just users is the submodule at `/app/routers/users.py`.

You want to have the *path operations* related to your users separated from the rest of the code, to keep it organized.

But it's still part of the same **FastAPI** application/web API (it's part of the same "Python Package").

You can create the *path operations* for that module using `APIRouter`.

### Import `APIRouter` { #import-apirouter }

     * are used to distinguish the various services on a host. <a
     * href="../../../nbtcodes.html">Here</a> is
     * a fairly complete list of NetBIOS hex codes. Scope is not used but is
     * still functional in other NetBIOS products and so for completeness it has been
     * implemented. A <code>scope</code> of <code>null</code> or <code>""</code>
     * signifies no scope.
     *

 * rarely use it directly, in part because it does not provide direct access to the {@code Future}
 * result. (If you want such access, you may prefer {@link Futures#addCallback
 * Futures.addCallback}.) Still, direct {@code addListener} calls are occasionally useful:
 *
 * {@snippet :
 * final String name = ...;
 * inFlight.add(name);
 * ListenableFuture<Result> future = service.query(name);

  with default values defined in {{{../../compat/maven-resolver-provider/apidocs/org/apache/maven/repository/internal/type/DefaultTypeProvider.html}DefaultTypeProvider}}.

  For compatibility, legacy Maven 3 artifact handlers are still provided:

*--------------------+---------------+------------+------------+-----------+---------------------+-----------------------+

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