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")

          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)
          }
        }

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".

```Python hl_lines="2"
# This is not asynchronous
def get_sequential_burgers(number: int):
    # Do some sequential stuff to create the burgers
    return burgers
```

With `async def`, Python knows that, inside that function, it has to be aware of `await` expressions, and that it can "pause" ⏸ the execution of that function and go do something else 🔀 before coming back.

## 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"

!!! check
    Notice that you don't have to create a special class and pass it somewhere to **FastAPI** to "register" it or anything similar.

    You just pass it to `Depends` and **FastAPI** knows how to do the rest.

## Share `Annotated` dependencies

In the examples above, you see that there's a tiny bit of **code duplication**.

          .url("http://" + SocksProxy.HOSTNAME_THAT_ONLY_THE_PROXY_KNOWS + ":" + server.port)
          .build(),
      )
    val response = call.execute()
    assertThat(response.code).isEqualTo(200)
    response.body.close()
    val expectedAddress =
      InetSocketAddress.createUnresolved(
        SocksProxy.HOSTNAME_THAT_ONLY_THE_PROXY_KNOWS,
        server.port,
      )

 * Self-signed Signature: 799f1d96c6b6793f228d87d3870304606a6b9a2e59897311ac43d1f513ff8d392bc0f...
 * ```
 *
 * In this example the HTTP client already knows and trusts the last certificate, "Entrust Root
 * Certification Authority - G2". That certificate is used to verify the signature of the
 * intermediate certificate, "Entrust Certification Authority - L1M". The intermediate certificate

**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"

   */
  @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(