t.Once.Do(func() {
		t.ttl = ttl
		t.updateFn = update
		t.opts = opts
	})
}

// GetWithCtx will return a cached value or fetch a new one.
// passes a caller context, if caller context cancels nothing
// is cached.
// If the Update function returns an error the value is forwarded as is and not cached.
func (t *Cache[T]) GetWithCtx(ctx context.Context) (T, error) {

// SSE-C.
func (ssec) IsEncrypted(metadata map[string]string) bool {
	if _, ok := metadata[MetaSealedKeySSEC]; ok {
		return true
	}
	return false
}

// ParseHTTP parses the SSE-C headers and returns the SSE-C client key
// on success. SSE-C copy headers are ignored.
func (ssec) ParseHTTP(h http.Header) (key [32]byte, err error) {

<img src="/img/tutorial/extending-openapi/image04.png">

## Change Default Swagger UI Parameters

FastAPI includes some default configuration parameters appropriate for most of the use cases.

It includes these default configurations:

{* ../../fastapi/openapi/docs.py ln[8:23] hl[17:23] *}

You can override any of them by setting a different value in the argument `swagger_ui_parameters`.

   *
   * <p>For the case of {@link RoundingMode#HALF_EVEN}, this implementation uses the IEEE 754
   * default rounding mode: if the two nearest representable values are equally near, the one with
   * the least significant bit zero is chosen. (In such cases, both of the nearest representable
   * values are even integers; this method returns the one that is a multiple of a greater power of
   * two.)

 * created for testing should have Integer node and String edge objects.
 *
 * <p>Test cases that should be handled similarly in any graph implementation are included in this
 * class. For example, testing that {@code nodes()} method returns the set of the nodes in the
 * graph. The following test cases are left for the subclasses to handle:
 *
 * <ul>
 *   <li>Test cases related to whether the graph is directed, undirected, mutable, or immutable.

		if paddinglen == 0 {
			seq = append(seq, fmt.Sprintf("%d", i))
		} else {
			seq = append(seq, fmt.Sprintf(fmt.Sprintf("%%0%dd", paddinglen), i))
		}
	}
	return seq
}

// Test tests parses endpoint ellipses input pattern.
func TestParseEndpointSet(t *testing.T) {
	testCases := []struct {
		arg     string
		es      endpointSet
		success bool
	}{
		// Tests invalid inputs.
		{
			"...",

   *       CacheLoader#loadAll bulk loading implementations}
   * </ul>
   *
   * <p><b>Warning:</b> For any given key, every {@code loader} used with it should compute the same
   * value. Otherwise, a call that passes one {@code loader} may return the result of another call
   * with a differently behaving {@code loader}. For example, a call that requests a short timeout

You can see the query parameters in the docs UI at `/docs`:

<div class="screenshot">
<img src="/img/tutorial/query-param-models/image01.png">
</div>

## Forbid Extra Query Parameters

In some special use cases (probably not very common), you might want to **restrict** the query parameters that you want to receive.

You can use Pydantic's model configuration to `forbid` any `extra` fields:

//// tab | Python 3.10+

        * So, the user will have to log in again at some point later.
        * And if the token is stolen, the risk is less. It is not like a permanent key that will work forever (in most of the cases).
* The frontend stores that token temporarily somewhere.
* The user clicks in the frontend to go to another section of the frontend web app.
* The frontend needs to fetch some more data from the API.

      }
    }

    static final CancellationException cancellationExceptionWithCause(
        @Nullable String message, @Nullable Throwable cause) {
      CancellationException exception = new CancellationException(message);
      exception.initCause(cause);
      return exception;
    }
  }