**FastAPI** est totalement basé sur ces annotations de type, qui lui donnent de nombreux avantages.

Mais même si vous n'utilisez pas ou n'utiliserez jamais **FastAPI**, vous pourriez bénéficier d'apprendre quelques choses sur ces dernières.

/// note

Si vous êtes un expert Python, et que vous savez déjà **tout** sur les annotations de type, passez au chapitre suivant.

///

## Motivations

Prenons un exemple simple :

   * execute. If execution has already begun, the listener is executed immediately.
   *
   * <p>When selecting an executor, note that {@code directExecutor} is dangerous in some cases. See
   * the discussion in the {@link ListenableFuture#addListener ListenableFuture.addListener}
   * documentation.
   */
  public void add(Runnable runnable, Executor executor) {

    // that simply loops through the subscribers and dispatches the event to each would actually
    // probably provide a stronger order guarantee, though that order would obviously be different
    // in some cases.

    /** Global event queue. */
    private final ConcurrentLinkedQueue<EventWithSubscriber> queue =
        Queues.newConcurrentLinkedQueue();

    @Override

	case errFaultyDisk.Error():
		return errFaultyDisk
	case errFaultyRemoteDisk.Error():
		return errFaultyRemoteDisk
	case errFileCorrupt.Error():
		return errFileCorrupt
	case errUnexpected.Error():
		return errUnexpected
	case errDiskFull.Error():
		return errDiskFull
	case errVolumeNotFound.Error():
		return errVolumeNotFound
	case errVolumeExists.Error():
		return errVolumeExists

    firstException = expected;
    // Second time should also fail, with a cached causal chain.
    expected = assertThrows(PotentialDeadlockException.class, () -> lockA.lock());
    checkMessage(expected, "LockB -> LockA", "LockA -> LockB");
    // The causal chain should be cached.
    assertSame(firstException.getCause(), expected.getCause());
    // lockA should work after lockB is released.

    firstException = expected;
    // Second time should also fail, with a cached causal chain.
    expected = assertThrows(PotentialDeadlockException.class, () -> lockA.lock());
    checkMessage(expected, "LockB -> LockA", "LockA -> LockB");
    // The causal chain should be cached.
    assertSame(firstException.getCause(), expected.getCause());
    // lockA should work after lockB is released.

		}
	}

	// Test cases for signature-V4.
	testCasesV4 := []struct {
		objectName         string
		data               []byte
		expectedHeaders    map[string]string
		expectedRespStatus int
		accessKey          string
		secretKey          string
		malformedBody      bool
	}{
		// Success case.
		{
			objectName:         "test",

        }
    }

    private void handleChecksumFailure(String checksumPolicy, String message, Throwable cause)
            throws ChecksumFailedException {
        if (ArtifactRepositoryPolicy.CHECKSUM_POLICY_FAIL.equals(checksumPolicy)) {
            throw new ChecksumFailedException(message, cause);
        } else if (!ArtifactRepositoryPolicy.CHECKSUM_POLICY_IGNORE.equals(checksumPolicy)) {

/// tip

You could use any other SQL or NoSQL database library you want (in some cases called <abbr title="Object Relational Mapper, a fancy term for a library where some classes represent SQL tables and instances represent rows in those tables">"ORMs"</abbr>), FastAPI doesn't force you to use anything. 😎

///

          }
        };
    AssertionError actual = null;
    try {
      tester.test();
    } catch (AssertionError e) {
      actual = e;
    }
    assertNotNull("verify() should be able to cause test failure", actual);
    assertTrue(
        "AssertionError should have info about why test failed",
        actual.getCause().getMessage().contains(message));
  }

  public void testMissingException() {