## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

```Python hl_lines="9-13  36-53"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip

  // stomped by the controller.
  // +optional
  optional AggregationRule aggregationRule = 3;
}

// ClusterRoleBinding references a ClusterRole, but not contain it.  It can reference a ClusterRole in the global namespace,
// and adds who information via Subject.
// Deprecated in v1.17 in favor of rbac.authorization.k8s.io/v1 ClusterRoleBinding, and will no longer be served in v1.22.

  // stomped by the controller.
  // +optional
  optional AggregationRule aggregationRule = 3;
}

// ClusterRoleBinding references a ClusterRole, but not contain it.  It can reference a ClusterRole in the global namespace,
// and adds who information via Subject.
// Deprecated in v1.17 in favor of rbac.authorization.k8s.io/v1 ClusterRoleBinding, and will no longer be served in v1.22.

          /*
           * standardToArray returns `@Nullable Object[]` rather than `Object[]` but only because it
           * can be used with collections that may contain null. This collection is a collection of
           * non-null Entry objects (Entry objects that might contain null values but are not
           * themselves null), so we can treat it as a plain `Object[]`.
           */
          @SuppressWarnings("nullness")

			// validation needed.
			continue
		case !strings.Contains(output, line1):
			t.Errorf("Testcase %d: output '%s' did not contain line 1: '%s'", i+1, output, line1)
		case !strings.Contains(output, line2):
			t.Errorf("Testcase %d: output '%s' did not contain line 2: '%s'", i+1, output, line2)
		}
	}

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hartan
hau
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hauetan
hemen
hemendik
hemengo
hi
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honela
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horretan
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nor
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  }

  /**
   * Computes or retrieves the values corresponding to {@code keys}. This method is called by {@link
   * LoadingCache#getAll}.
   *
   * <p>If the returned map doesn't contain all requested {@code keys} then the entries it does
   * contain will be cached, but {@code getAll} will throw an exception. If the returned map
   * contains extra keys not present in {@code keys} then all returned entries will be cached, but

        Map artifactMap = project.getArtifactMap();

        assertNotNull( artifactMap, "artifact-map should not be null." );
        assertEquals( 1, artifactMap.size(), "artifact-map should contain 1 element." );

        Artifact artifact = (Artifact) artifactMap.get( key );

        assertNotNull( artifact, "dependency artifact not found in map." );

| `terms_of_service` | `str` | A URL to the Terms of Service for the API. If provided, this has to be a URL. |

		return err
	}

	// Validate that matching clientID appears in the aud or azp claims.

	// REQUIRED. Audience(s) that this ID Token is intended for.
	// It MUST contain the OAuth 2.0 client_id of the Relying Party
	// as an audience value. It MAY also contain identifiers for
	// other audiences. In the general case, the aud value is an
	// array of case sensitive strings. In the common special case