## An app with callbacks

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

# https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#creating-issue-forms
# https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/syntax-for-githubs-form-schema
name: Bugs
description: The go command, standard library, or anything else
title: "import/path: issue title"

body:
  - type: markdown
    attributes:

    // requireNonNull accommodates Android's @RecentlyNullable annotation on ThreadLocal.get
    return requireNonNull(DEST_TL.get());
  }

  /**
   * A thread-local destination buffer to keep us from creating new buffers. The starting size is
   * 1024 characters. If we grow past this we don't put it back in the threadlocal, we just keep
   * going and grow as needed.
   */
  private static final ThreadLocal<char[]> DEST_TL =

	// HTTP request for testing when `objectLayer` is set to `nil`.
	// There is no need to use an existing bucket and valid input for creating the request
	// since the `objectLayer==nil`  check is performed before any other checks inside the handlers.
	// The only aim is to generate an HTTP request in a way that the relevant/registered end point is evoked/called.

 * in the case of Android, the current app. If that is not possible (as is the case under the very
 * old Android Ice Cream Sandwich release), then this class throws an exception instead of creating
 * a file or directory that would be more accessible.
 */
@J2ktIncompatible
@GwtIncompatible
@J2ObjCIncompatible
@ElementTypesAreNonnullByDefault
abstract class TempFileCreator {

 *
 * @author David Beaumont
 * @since 15.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class ArrayBasedEscaperMap {
  /**
   * Returns a new ArrayBasedEscaperMap for creating ArrayBasedCharEscaper or
   * ArrayBasedUnicodeEscaper instances.
   *
   * @param replacements a map of characters to their escaped representations
   */

To configure them, pass the `swagger_ui_parameters` argument when creating the `FastAPI()` app object or to the `get_swagger_ui_html()` function.

`swagger_ui_parameters` receives a dictionary with the configurations passed to Swagger UI directly.

This is necessary for bookkeeping when creating new streams. Correct framing requires that stream IDs are sequential on the socket, so we need to bundle assigning the ID with sending the `SYN_STREAM` frame.

## Connection Pool

import okhttp3.Protocol
import okio.BufferedSource

/**
 * [HTTP/2][Protocol.HTTP_2] only. Processes server-initiated HTTP requests on the client.
 * Implementations must quickly dispatch callbacks to avoid creating a bottleneck.
 *
 * While [onReset] may occur at any time, the following callbacks are expected in order,
 * correlated by stream ID.
 *
 *  * [onRequest]
 *  * [onHeaders] (unless canceled)

   */
  // TODO(user): Evaluate whether it makes sense to always piggyback the computation of a
  // HashCode on an existing OutputStream, compared to creating a separate OutputStream that could
  // be (optionally) be combined with another if needed (with something like
  // MultiplexingOutputStream).
  public HashingOutputStream(HashFunction hashFunction, OutputStream out) {