## Optional parameters { #optional-parameters }

The same way, you can declare optional query parameters, by setting their default to `None`:

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

In this case, the function parameter `q` will be optional, and will be `None` by default.

/// check

                    switch (type) {
                        case INITIATED:
                            delegate.transferInitiated(transferEvent);
                            break;
                        case STARTED:
                            delegate.transferStarted(transferEvent);
                            break;
                        case PROGRESSED:

            }
        } else {
            type = parseStorageType(typeStr);
        }

        switch (type) {
        case GCS:
            return new GcsStorageClient(fessConfig.getStorageProjectId(), bucket, endpoint, fessConfig.getStorageCredentialsPath());
        case S3:
        case S3_COMPAT:
        default:
            return new S3StorageClient(endpoint, accessKey, secretKey, bucket, fessConfig.getStorageRegion());

            case WitnessAsyncNotifyMessage.WitnessNotificationMessage.WITNESS_CLIENT_MOVE:
            case WitnessAsyncNotifyMessage.WitnessNotificationMessage.WITNESS_SHARE_MOVE:
                if (message.getDestinationNode() != null) {
                    notification.setNewNodeAddress(message.getDestinationNode());
                }
                break;

		switch k := priv.(type) {
		case *rsa.PrivateKey:
			return &k.PublicKey
		case *ecdsa.PrivateKey:
			return &k.PublicKey
		default:
			return nil
		}
	}

	pemBlockForKey := func(priv any) *pem.Block {
		switch k := priv.(type) {
		case *rsa.PrivateKey:
			return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(k)}
		case *ecdsa.PrivateKey:

// set new encryption metadata from http request headers for SSE-C and generated key from KMS in the case of
// SSE-S3
func setEncryptionMetadata(r *http.Request, bucket, object string, metadata map[string]string) (err error) {
	var (
		key    []byte
		keyID  string
		kmsCtx kms.Context
	)
	kind, _ := crypto.IsRequested(r.Header)
	switch kind {
	case crypto.SSEC:
		key, err = ParseSSECustomerRequest(r)
		if err != nil {

	r, w := 0, 0
	if rooted {
		r, w = 1, 1
	}

	for r < n {
		switch {
		case path[r] > 127:
			// Non ascii.
			return true
		case path[r] == '/':
			// multiple / elements
			return true
		case path[r] == '.' && (r+1 == n || path[r+1] == '/'):
			// . element - assume it has to be cleaned.
			return true
		case path[r] == '.' && path[r+1] == '.' && (r+2 == n || path[r+2] == '/'):

        @Override
        public ModelSource resolveModel(Dependency dependency) throws UnresolvableModelException {
            return switch (dependency.getManagementKey()) {
                case BASE1_ID -> new StringModelSource(BASE1);
                case BASE2_ID -> new StringModelSource(BASE2);
                default -> null;
            };
        }
    }

    static class BaseModelResolver implements ModelResolver {

	for {
		var (
			ok    bool
			entry any
		)

		if count < h.batchSize {
			tickered := false
			select {
			case <-ticker.C:
				tickered = true
			case entry = <-globalBuffer:
			case entry, ok = <-h.logCh:
				if !ok {
					return
				}
			case <-ctx.Done():
				return
			}

			if !tickered {
				h.totalMessages.Add(1)
				if !isDirQueue {

	// fmt.Printf("actual: %v offset: %v (%v) whence: %v\n", rsc.size, offset, rsc.offset, whence)
	switch whence {
	case io.SeekStart:
		rsc.offset = offset
	case io.SeekCurrent:
		rsc.offset += offset
	case io.SeekEnd:
		rsc.offset = rsc.size + offset
	}
	if rsc.offset < 0 {
		return rsc.offset, errors.New("seek to invalid negative offset")
	}