* non-null, it should be reported to the user should all further attempts fail.
   *
   * The two values are independent: results can contain both (recoverable error), neither
   * (success), just an exception (permanent failure), or just a plan (non-exceptional retry).
   */
  data class ConnectResult(
    val plan: Plan,
    val nextPlan: Plan? = null,
    val throwable: Throwable? = null,
  ) {
    val isSuccess: Boolean

# About HTTPS { #about-https }

It is easy to assume that HTTPS is something that is just "enabled" or not.

But it is way more complex than that.

/// tip

If you are in a hurry or don't care, continue with the next sections for step by step instructions to set everything up with different techniques.

///

They are just a convenience, they hold the same number, but that way you can use the editor's autocomplete to find them:

<img src="/img/tutorial/response-status-code/image02.png">

/// note | Technical Details

You could also use `from starlette import status`.

          // In the case of a concurrent remove, we might observe a zero value, which means another
          // thread is about to remove (element, existingCounter) from the map. Rather than wait,
          // we can just do that work here.
          AtomicInteger newCounter = new AtomicInteger(occurrences);
          if ((countMap.putIfAbsent(element, newCounter) == null)
              || countMap.replace(element, existingCounter, newCounter)) {

  public void testVisibility() {
    // Just check we can run code that depends on OkHttp types
    OkHttpCaller.callOkHttp(HttpUrl.get("https://square.com/robots.txt"));
  }

  @Test
  public void testMockWebServer() throws IOException {
    MockWebServer server = new MockWebServer();
    server.enqueue(new MockResponse(200, Headers.of(), "Hello, Java9!"));
    server.start();

    // Just check we can run code that depends on OkHttp types

Here we do it... just to show that we can 🤷:

{* ../../docs_src/bigger_applications/app_an_py39/main.py hl[21:23] title["app/main.py"] *}

and it will work correctly, together with all the other *path operations* added with `app.include_router()`.

/// info | Very Technical Details

**Note**: this is a very technical detail that you probably can **just skip**.

---

# as other tools that use them depend on that
# Ref: https://github.com/fastapi/fastapi/pull/14320

from fastapi import Depends, Security


def dep():
    pass


def test_depends_hashable():
    dep()  # just for coverage
    d1 = Depends(dep)
    d2 = Depends(dep)
    d3 = Depends(dep, scope="function")
    d4 = Depends(dep, scope="function")

    s1 = Security(dep)
    s2 = Security(dep)

Because all the **fields actually change** (the type now includes `None` and they now have a default value of `None`), we need to **re-declare** them.

 * @since 20.0
 */
@Beta
public interface MutableNetwork<N, E> extends Network<N, E> {

  /**
   * Adds {@code node} if it is not already present.
   *
   * <p><b>Nodes must be unique</b>, just as {@code Map} keys must be. They must also be non-null.
   *
   * @return {@code true} if the network was modified as a result of this call
   */
  @CanIgnoreReturnValue
  boolean addNode(N node);

  /**

For example, if you want to read or manipulate the request body before it is processed by your application.

/// danger

This is an "advanced" feature.

If you are just starting with **FastAPI** you might want to skip this section.

///

## Use cases { #use-cases }

Some use cases include: