* </ul>
     *
     * @param relPath is the path of the requested model source relative to this model source POM.
     * @return related model source or <code>null</code> if no such model source.
     */
    ModelSource2 getRelatedSource(String relPath);

    /**
     * Returns location of the POM, never <code>null</code>.
     */
    URI getLocationURI();

And Pydantic's `Field` returns an instance of `FieldInfo` as well.

`Body` also returns objects of a subclass of `FieldInfo` directly. And there are others you will see later that are subclasses of the `Body` class.

Remember that when you import `Query`, `Path`, and others from `fastapi`, those are actually functions that return special classes.

///

/// tip

### Use cases: external service { #use-cases-external-service }

An example could be that you have an external authentication provider that you need to call.

You send it a token and it returns an authenticated user.

This provider might be charging you per request, and calling it might take some extra time than if you had a fixed mock user for tests.

     * @return an OptionalEntity containing the file configuration if found, empty otherwise
     */
    public OptionalEntity<FileConfig> getFileConfig(final String id) {
        return fileConfigBhv.selectByPK(id);
    }

    /**
     * Retrieves a file configuration by its name.
     * If multiple configurations exist with the same name, returns the first one
     * ordered by sort order.

     */
    private samr() {
        // Utility class
    }

    /**
     * Returns the RPC interface syntax UUID and version for SAMR protocol.
     *
     * @return The SAMR interface UUID string
     */
    public static String getSyntax() {
        return "12345778-1234-abcd-ef00-0123456789ac:1.0";
    }

    /** Account control bit flag: Account is disabled */

     */
    private samr() {
        // Utility class
    }

    /**
     * Returns the RPC interface syntax UUID and version for SAMR protocol.
     *
     * @return The SAMR interface UUID string
     */
    public static String getSyntax() {
        return "12345778-1234-abcd-ef00-0123456789ac:1.0";
    }

    /** Account control bit flag: Account is disabled */

FastAPI usa un **ID único** para cada *path operation*, se usa para el **operation ID** y también para los nombres de cualquier modelo personalizado necesario, para requests o responses.

Puedes personalizar esa función. Toma un `APIRoute` y retorna un string.

Por ejemplo, aquí está usando el primer tag (probablemente tendrás solo un tag) y el nombre de la *path operation* (el nombre de la función).

        assertEquals("Invalid resume key", exception.getMessage(), "Exception message should match");
    }

    @Test
    @DisplayName("Test getResumeKey returns null before decode")
    void testGetResumeKeyBeforeDecode() {
        assertNull(response.getResumeKey(), "Resume key should be null before decode");
    }

    @Test

        // Add individual filters
        service.addIncludeUrlFilter(sessionId, "https://sample.org/.*");
        service.addExcludeUrlFilter(sessionId, "https://example.com/secret/.*");

        // Setup mock returns
        List<Pattern> mockIncludePatterns = new ArrayList<>();
        mockIncludePatterns.add(Pattern.compile("https://example.com/.*"));
        mockIncludePatterns.add(Pattern.compile("https://test.com/.*"));

    assertThat(eventRecorder.recordedEventTypes()).isEqualTo(expectedEvents)

    // Confirm that the connection pool was not corrupted by making another call.
    makeSimpleCall()
  }

  /**
   * If the server returns a full response, it doesn't really matter if the HTTP/2 stream is reset.
   * Attempts to write the request body fails fast.
   */
  @Test
  fun serverTruncatesRequestHttp2OnDuplexRequest() {