val domainName = fromSource.readUtf8(domainNameLength.toLong())
          // Resolve HOSTNAME_THAT_ONLY_THE_PROXY_KNOWS to localhost.
          when {
            domainName.equals(HOSTNAME_THAT_ONLY_THE_PROXY_KNOWS, ignoreCase = true) -> {
              InetAddress.getByName("localhost")
            }
            else -> InetAddress.getByName(domainName)
          }
        }

   * elements than the collection), the element in the array immediately following the end of the
   * collection is set to {@code null}. This is useful in determining the length of the collection
   * <i>only</i> if the caller knows that the collection does not contain any null elements.
   *
   * <p>This method returns the elements in the order they are returned by the collection's
   * iterator.
   *

    Class<E> result = classOrNull == null ? (Class<E>) (Class<?>) Object.class : classOrNull;
    return result;
  }

  /*
   * If I understand correctly:
   *
   * This needs to be a @JsMethod so that J2CL knows to look for a JavaScript implemention of
   * it in Platform.native.js. (The JavaScript implementation inline below is visible to *GWT*, but
   * *J2CL* doesn't look at it.)
   *

      clientTestRule.newClientBuilder()
        .proxy(socksProxy.proxy())
        .build()
    val url =
      server.url("/")
        .newBuilder()
        .host(SocksProxy.HOSTNAME_THAT_ONLY_THE_PROXY_KNOWS)
        .build()
    val request = Request.Builder().url(url).build()
    val response1 = client.newCall(request).execute()
    assertThat(response1.body.string()).isEqualTo("abc")

   */
  @Throws(IOException::class)
  fun authenticate(
    route: Route?,
    response: Response,
  ): Request?

  companion object {
    /** An authenticator that knows no credentials and makes no attempt to authenticate. */
    @JvmField
    val NONE: Authenticator = AuthenticatorNone()

    private class AuthenticatorNone : Authenticator {
      override fun authenticate(

**FastAPI** knows what to do in each case and how to re-use the same object, so that all the background tasks are merged together and are run in the background afterwards:

=== "Python 3.10+"

    ```Python hl_lines="13  15  22  25"

<img src="/img/tutorial/response-status-code/image01.png">

!!! note
    Some response codes (see the next section) indicate that the response does not have a body.

    FastAPI knows this, and will produce OpenAPI docs that state there is no response body.

## About HTTP status codes

!!! note
    If you already know what HTTP status codes are, skip to the next section.

## Multiple path and query parameters

You can declare multiple path parameters and query parameters at the same time, **FastAPI** knows which is which.

And you don't have to declare them in any specific order.

They will be detected by name:

=== "Python 3.10+"

    ```Python hl_lines="6  8"

if "johndoe" == "stanleyjobson" and "love123" == "swordfish":
    ...
```

But right at the moment Python compares the first `j` in `johndoe` to the first `s` in `stanleyjobson`, it will return `False`, because it already knows that those two strings are not the same, thinking that "there's no need to waste more computation comparing the rest of the letters". And your application will say "Incorrect username or password".