type Singleton[T any] struct {
	v   *T
	set chan struct{}
}

// NewSingleton creates a new unset singleton.
func NewSingleton[T any]() *Singleton[T] {
	return &Singleton[T]{set: make(chan struct{}), v: nil}
}

// Get will return the singleton value.
func (s *Singleton[T]) Get() *T {
	<-s.set
	return s.v
}

// GetNonBlocking will return the singleton value or nil if not set yet.

forth). A Go function called by C code may take C pointers as arguments,
and it may store non-pointer data, C pointers, or Go pointers to pinned
memory through those pointers. It may not store a Go pointer to unpinned
memory in memory pointed to by a C pointer (which again, implies that it
may not store a string, slice, channel, and so forth). A Go function
called by C code may take a Go pointer but it must preserve the property

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package okhttp3.slack;

/** Authorization for an application to make Slack API calls on behalf of a user. */
@SuppressWarnings("checkstyle:membername")
public final class OAuthSession {
  public final boolean ok;
  public final String access_token;
  public final String scope;

	}
	minor, err := strconv.Atoi(minors)
	if err != nil {
		return nil, fmt.Errorf("minor version is not a number: %v", minors)
	}

	var messages diag.Messages = make([]diag.Message, 0)

	if minor <= 21 {
		// ENHANCED_RESOURCE_SCOPING
		if err := checkPilot(cli, ctx.IstioNamespace(), &messages); err != nil {
			return nil, err
		}
	}
	if minor <= 21 {

    }

    /**
     * Throws {@link UnsupportedOperationException}. This method is inherited from {@link
     * ImmutableMap.Builder}, but it does not make sense for bimaps.
     *
     * @throws UnsupportedOperationException always
     * @deprecated This method does not make sense for bimaps and should not be called.
     * @since 31.1
     */
    @DoNotCall
    @Deprecated
    @Override

The following arguments are supported:

* `allow_origins` - A list of origins that should be permitted to make cross-origin requests. E.g. `['https://example.org', 'https://www.example.org']`. You can use `['*']` to allow any origin.
* `allow_origin_regex` - A regex string to match against origins that should be permitted to make cross-origin requests. e.g. `'https://.*\.example\.org'`.

                    <mxGeometry x="-140" y="-75" width="500" height="350" as="geometry"/>
                </mxCell>

// It should never be used directly since buckets are
// distributed deterministically.
// Therefore no cluster locks are required.
var localMetacacheMgr = &metacacheManager{
	buckets: make(map[string]*bucketMetacache),
	trash:   make(map[string]metacache),
}

type metacacheManager struct {
	mu      sync.RWMutex
	init    sync.Once
	buckets map[string]*bucketMetacache
	trash   map[string]metacache // Recently deleted lists.

			if err != nil {
				err = msgp.WrapError(err, "Distribution")
				return
			}
			if cap(z.Distribution) >= int(zb0002) {
				z.Distribution = (z.Distribution)[:zb0002]
			} else {
				z.Distribution = make([]int, zb0002)
			}
			for za0001 := range z.Distribution {
				z.Distribution[za0001], err = dc.ReadInt()
				if err != nil {
					err = msgp.WrapError(err, "Distribution", za0001)
					return
				}
			}

When you declare a default value for non-path parameters (for now, we have only seen query parameters), then it is not required.

If you don't want to add a specific value but just make it optional, set the default as `None`.

But when you want to make a query parameter required, you can just not declare any default value:

```Python hl_lines="6-7"
{!../../docs_src/query_params/tutorial005.py!}
```