}

  @Override
  protected void expectMissing(Entry<K, V>... entries) {
    for (Entry<K, V> entry : entries) {
      assertFalse("Should not contain entry " + entry, actualContents().contains(entry));
      assertFalse(
          "Should not contain key " + entry.getKey() + " mapped to value " + entry.getValue(),
          equal(getMap().get(entry.getKey()), entry.getValue()));
    }
  }

      BiMap<V, K> inv = getMap().inverse();
      assertFalse(
          "Inverse should not contain entry " + reversed, inv.entrySet().contains(reversed));
      assertFalse(
          "Inverse should not contain key " + reversed.getKey(),
          inv.containsKey(reversed.getKey()));
      assertFalse(
          "Inverse should not contain value " + reversed.getValue(),
          inv.containsValue(reversed.getValue()));
      /*

    assertThrows(NullPointerException.class, () -> getMap().putIfAbsent(null, v3()));
    expectUnchanged();
    expectNullKeyMissingWhenNullKeysUnsupported(
        "Should not contain null key after unsupported putIfAbsent(null, value)");
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPutIfAbsent_nullValueUnsupportedAndKeyAbsent() {

    }

    private void assertContains(VersionRange range, String version) {
        assertTrue(range.contains(newVersion(version)), range + " should contain " + version);
    }

    private void assertNotContains(VersionRange range, String version) {
        assertFalse(range.contains(newVersion(version)), range + " should not contain " + version);
    }

    @Test
    void testLowerBoundInclusiveUpperBoundInclusive() {

  }

  @Override
  protected void expectMissing(Entry<K, V>... entries) {
    for (Entry<K, V> entry : entries) {
      assertFalse("Should not contain entry " + entry, actualContents().contains(entry));
      assertFalse(
          "Should not contain key " + entry.getKey() + " mapped to value " + entry.getValue(),
          equal(getMap().get(entry.getKey()), entry.getValue()));
    }
  }

## 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

      BiMap<V, K> inv = getMap().inverse();
      assertFalse(
          "Inverse should not contain entry " + reversed, inv.entrySet().contains(reversed));
      assertFalse(
          "Inverse should not contain key " + reversed.getKey(),
          inv.containsKey(reversed.getKey()));
      assertFalse(
          "Inverse should not contain value " + reversed.getValue(),
          inv.containsValue(reversed.getValue()));
      /*

		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

    assertThrows(NullPointerException.class, () -> getMap().putIfAbsent(null, v3()));
    expectUnchanged();
    expectNullKeyMissingWhenNullKeysUnsupported(
        "Should not contain null key after unsupported putIfAbsent(null, value)");
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPutIfAbsent_nullValueUnsupportedAndKeyAbsent() {

    assertTrue(
        "addAll(somePresent) should return true",
        collection.addAll(MinimalCollection.of(e3(), e0())));
    assertTrue("should contain " + e3(), collection.contains(e3()));
    assertTrue("should contain " + e0(), collection.contains(e0()));
  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  public void testAddAll_unsupportedSomePresent() {