And **your users** define in some way (for example in a web dashboard somewhere) the **URL** where your app should send those requests.

All the **logic** about how to register the URLs for webhooks and the code to actually send those requests is up to you. You write it however you want to in **your own code**.

pkg testing, type TB interface, Setenv(string, string)
pkg text/template/parse, const SkipFuncCheck = 2
pkg text/template/parse, const SkipFuncCheck Mode
pkg time, const Layout = "01/02 03:04:05PM '06 -0700"
pkg time, const Layout ideal-string
pkg time, func UnixMicro(int64) Time
pkg time, func UnixMilli(int64) Time
pkg time, method (Time) GoString() string
pkg time, method (Time) IsDST() bool

The benefit of raising an exception over returning a value will be more evident in the section about Dependencies and Security.

In this example, when the client requests an item by an ID that doesn't exist, raise an exception with a status code of `404`:

{* ../../docs_src/handling_errors/tutorial001.py hl[11] *}

import java.net.URISyntaxException;
import java.net.URL;
import java.util.Arrays;

import org.apache.maven.api.Session;
import org.apache.maven.artifact.repository.ArtifactRepository;
import org.apache.maven.artifact.repository.layout.ArtifactRepositoryLayout;
import org.apache.maven.bridge.MavenRepositorySystem;
import org.apache.maven.execution.DefaultMavenExecutionRequest;
import org.apache.maven.execution.DefaultMavenExecutionResult;

# and it does not seem possible to e.g. copy "gs://foo/bar" as anything other than
# "/path/bar". This script uses "gsutil rsync" instead, which acts on directory
# contents. About arguments to gsutil:
# "gsutil -m rsync" runs in parallel.
# "gsutil rsync -r" is recursive and makes directories work.
# "gsutil rsync -d" is "sync and delete files from destination if not present in source"

{
    "X-Token values": [
        "bar",
        "foo"
    ]
}
```

## Recap { #recap }

Declare headers with `Header`, using the same common pattern as `Query`, `Path` and `Cookie`.

    assumeFalse(windows, "This test fails on Windows.")
  }

  @JvmStatic
  val windows: Boolean
    get() = System.getProperty("os.name", "?").startsWith("Windows")

  /**
   * Make assertions about the suppressed exceptions on this. Prefer this over making direct calls
   * so tests pass on GraalVM, where suppressed exceptions are silently discarded.
   *
   * https://github.com/oracle/graal/issues/3008
   */

```

The second version is an "absolute import":

```Python
from app.routers import items, users
```

To learn more about Python Packages and Modules, read <a href="https://docs.python.org/3/tutorial/modules.html" class="external-link" target="_blank">the official Python documentation about Modules</a>.

///

### Avoid name collisions { #avoid-name-collisions }

      isTlsFallback = isTlsFallback,
    )

  override fun connectTcp(): ConnectResult {
    check(rawSocket == null) { "TCP already connected" }

    var success = false

    // Tell the call about the connecting call so async cancels work.
    user.addPlanToCancel(this)
    try {
      user.connectStart(route)

      connectSocket()
      success = true
      return ConnectResult(plan = this)

It doesn't matter. **FastAPI** will know what to do.

/// note

If you don't know, check the [Async: *"In a hurry?"*](../../async.md#in-a-hurry){.internal-link target=_blank} section about `async` and `await` in the docs.

///

## Integrated with OpenAPI { #integrated-with-openapi }