in.peek = true
		in.Push(NewSlice(in.Base(), in.Line(), []Token{Make(macroName, macro.name)}))
		return
	}
	actuals := in.argsFor(macro)
	var tokens []Token
	for _, tok := range macro.tokens {
		if tok.ScanToken != scanner.Ident {
			tokens = append(tokens, tok)
			continue
		}
		substitution := actuals[tok.text]
		if substitution == nil {
			tokens = append(tokens, tok)
			continue
		}

The webhooks that you define will end up in the **OpenAPI** schema and the automatic **docs UI**.

/// info

The `app.webhooks` object is actually just an `APIRouter`, the same type you would use when structuring your app with multiple files.

///

///

The only new thing is the `callbacks=invoices_callback_router.routes` as an argument to the *path operation decorator*. We'll see what that is next.

## Documenting the callback { #documenting-the-callback }

The actual callback code will depend heavily on your own API app.

And it will probably vary a lot from one app to the next.

It could be just one or two lines of code, like:

```Python

/**
 * Extracts the filename from the parameters as the content.
 *
 * <p>This extractor is useful when you want to index only the filename or resource name
 * without processing the actual file content. The input stream is validated but not
 * read - only the filename from the parameters is used as the extracted content.</p>
 *
 * <p>The filename is retrieved from the {@link ExtractData#RESOURCE_NAME_KEY} parameter.

* `name`
* `age`

{* ../../docs_src/sql_databases/tutorial002_an_py310.py ln[7:9] hl[7:9] *}

#### `Hero` - the *table model* { #hero-the-table-model }

Then let's create `Hero`, the actual *table model*, with the **extra fields** that are not always in the other models:

* `id`
* `secret_name`

    if (actual instanceof Collection) {
      contained = ((Collection<?>) actual).contains(expected);
    } else {
      for (Object o : actual) {
        if (equal(o, expected)) {
          contained = true;
          break;
        }
      }
    }

    if (!contained) {
      fail("Not true that " + actual + " contains " + expected);
    }
  }

      CacheBuilder<?, ?> expected, CacheBuilder<?, ?> actual) {
    assertWithMessage("concurrencyLevel")
        .that(actual.concurrencyLevel)
        .isEqualTo(expected.concurrencyLevel);
    assertWithMessage("expireAfterAccessNanos")
        .that(actual.expireAfterAccessNanos)
        .isEqualTo(expected.expireAfterAccessNanos);
    assertWithMessage("expireAfterWriteNanos")
        .that(actual.expireAfterWriteNanos)

    if (!Objects.equals(actual, expected)) {
      // fail(), but with the JUnit-supplied message.
      assertEquals("Using seed " + seed, expected, actual);
    }
  }

  private static void assertEqualsUsingStartedWith(
      Collection<?> startedWith, @Nullable Object expected, @Nullable Object actual) {
    if (!Objects.equals(actual, expected)) {

```

Using `Optional[str]` instead of just `str` will let the editor help you detect errors where you could be assuming that a value is always a `str`, when it could actually be `None` too.

`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

This also means that in Python 3.10, you can use `Something | None`:

//// tab | Python 3.10+

```Python hl_lines="1"

    if (actual instanceof Collection) {
      contained = ((Collection<?>) actual).contains(expected);
    } else {
      for (Object o : actual) {
        if (equal(o, expected)) {
          contained = true;
          break;
        }
      }
    }

    if (!contained) {
      fail("Not true that " + actual + " contains " + expected);
    }
  }