```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009_py39.py!}
```

Using `Optional[str]` instead of just `str` will let the editor help you detect errors where you could be assuming that a value is always a `str`, when it could actually be `None` too.

`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

* Retry 'connection refused' errors when setting up clusters on GCE. ([#57394](https://github.com/kubernetes/kubernetes/pull/57394), [@mborsz](https://github.com/mborsz))
* Retry 'connection refused' errors when setting up clusters on GCE. ([#57394](https://github.com/kubernetes/kubernetes/pull/57394), [@mborsz](https://github.com/mborsz))

    private List<CyclicDependencyException> circularDependencyExceptions;

    private List<ArtifactResolutionException> errorArtifactExceptions;

    // file system errors

    private List<ArtifactRepository> repositories;

    private Set<Artifact> requestedArtifacts;

    private Set<Artifact> artifacts;

    private MetadataGraph resolvedTree;

var erasureHealTests = []struct {
	dataBlocks, disks int

	// number of offline disks is also number of staleDisks for
	// erasure reconstruction in this test
	offDisks int

	// bad disks are online disks which return errors
	badDisks, badStaleDisks int

	blocksize, size int64
	algorithm       BitrotAlgorithm
	shouldFail      bool
}{

			return context.Cause(ctx)
		case newState := <-changed:
			if newState == StateConnected {
				return nil
			}
		}
	}
}

/*
var ErrDone = errors.New("done for now")

var ErrRemoteRestart = errors.New("remote restarted")


// Stateless connects to the remote handler and return all packets sent back.
// If the remote is restarted will return ErrRemoteRestart.

До FastAPI 0.106.0 вызывать исключения после `yield` было невозможно: код после `yield` в зависимостях выполнялся уже после отправки ответа, поэтому [Обработчики исключений](../tutorial/handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank} к тому моменту уже отработали.

    protected long executeTime;

    /** Total number of processed documents */
    protected long documentSize;

    /** Maximum number of indexer errors allowed */
    protected int maxIndexerErrorCount = 0;

    /** Maximum number of general errors allowed before termination */
    protected int maxErrorCount = 2;

    /** List of finished crawler session IDs for cleanup */

     *
     * @param paramMap the data store parameters
     * @param dataMap the document data to store
     * @throws DataStoreException if required fields are missing or other errors occur
     */
    @Override
    public void store(final DataStoreParams paramMap, final Map<String, Object> dataMap) {
        final SystemHelper systemHelper = ComponentUtil.getSystemHelper();

                System.arraycopy(data, offset + 8, addr, 0, 16);
                return InetAddress.getByAddress(addr);
            }
        } catch (Exception e) {
            // Ignore parsing errors
        }
        return null;
    }

    private boolean checkRSSCapability() {
        // Platform-specific RSS detection - simplified implementation
        try {

     */
    protected enum Result {
        /** Thumbnail was successfully generated */
        OK,
        /** Thumbnail generation failed due to processing errors */
        FAILED,
        /** Image dimensions do not meet validation requirements */
        INVALID_SIZE,
        /** No valid image data was found in the input */
        NO_IMAGE;
    }