<img src="/img/tutorial/sub-applications/image02.png">

If you try interacting with any of the two user interfaces, they will work correctly, because the browser will be able to talk to each specific app or sub-app.

### Technical Details: `root_path` { #technical-details-root-path }

    }

    @Override
    public List<String> getModelIds() {
        return modelIds;
    }

    public DefaultModelBuildingResult addModelId(String modelId) {
        // Intentionally notNull because Super POM may not contain a modelId
        Objects.requireNonNull(modelId, "modelId cannot null");

        modelIds.add(modelId);

        return this;
    }

    @Override
    public Model getRawModel() {

                buildTimestampFromGradleProperty.isPresent -> "from buildTimestamp property"
                runningInstallTask.get() -> "from current time because installing"
                runningDocsTestTask.get() -> "from current time because testing docs"
                runningOnCi.get() -> "from current time because CI"
                else -> "from current date"
            }
        }

    private

{* ../../docs_src/response_model/tutorial003_02_py39.py hl[8,10:11] *}

This simple case is handled automatically by FastAPI because the return type annotation is the class (or a subclass of) `Response`.

And tools will also be happy because both `RedirectResponse` and `JSONResponse` are subclasses of `Response`, so the type annotation is correct.

### Annotate a Response Subclass { #annotate-a-response-subclass }

      - name: Check links
        uses: lycheeverse/lychee-action@v2.7.0
        with:
          # excluded:
          # - notes.md and notes-templates.md - because they are a part of user guide
          # - Kotlin's Module.md - because it's a part of the Kotlin DSL docs
          args: >
            --no-progress --offline '**/*.md' --include-fragments

  /**
   * {@inheritDoc}
   *
   * <p>Because the values for a given key may have duplicates and follow the insertion ordering,
   * this method returns a {@link List}, instead of the {@link java.util.Collection} specified in
   * the {@link Multimap} interface.
   */
  @Override
  List<V> get(@ParametricNullness K key);

  /**
   * {@inheritDoc}
   *

  /**
   * {@inheritDoc}
   *
   * <p>Because the values for a given key may have duplicates and follow the insertion ordering,
   * this method returns a {@link List}, instead of the {@link java.util.Collection} specified in
   * the {@link Multimap} interface.
   */
  @Override
  List<V> get(@ParametricNullness K key);

  /**
   * {@inheritDoc}
   *

Because all the **fields actually change** (the type now includes `None` and they now have a default value of `None`), we need to **re-declare** them.

  /**
   * {@inheritDoc}
   *
   * <p>Because a {@code SetMultimap} has unique values for a given key, this method returns a
   * {@link Set}, instead of the {@link java.util.Collection} specified in the {@link Multimap}
   * interface.
   */
  @Override
  Set<V> get(@ParametricNullness K key);

  /**
   * {@inheritDoc}
   *

  /**
   * {@inheritDoc}
   *
   * <p>Because a {@code SetMultimap} has unique values for a given key, this method returns a
   * {@link Set}, instead of the {@link java.util.Collection} specified in the {@link Multimap}
   * interface.
   */
  @Override
  Set<V> get(@ParametricNullness K key);

  /**
   * {@inheritDoc}
   *