## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

```Python hl_lines="9-13  36-53"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip

| `terms_of_service` | `str` | A URL to the Terms of Service for the API. If provided, this has to be a URL. |

		return err
	}

	// Validate that matching clientID appears in the aud or azp claims.

	// REQUIRED. Audience(s) that this ID Token is intended for.
	// It MUST contain the OAuth 2.0 client_id of the Relying Party
	// as an audience value. It MAY also contain identifiers for
	// other audiences. In the general case, the aud value is an
	// array of case sensitive strings. In the common special case

   *
   * <p>Note: Non-bracketed IPv6 literals are allowed. Use {@link #requireBracketsForIPv6()} to
   * prohibit these.
   *
   * @param host the host string to parse. Must not contain a port number.
   * @param port a port number from [0..65535]
   * @return if parsing was successful, a populated HostAndPort object.

			// validation needed.
			continue
		case !strings.Contains(output, line1):
			t.Errorf("Testcase %d: output '%s' did not contain line 1: '%s'", i+1, output, line1)
		case !strings.Contains(output, line2):
			t.Errorf("Testcase %d: output '%s' did not contain line 2: '%s'", i+1, output, line2)
		}
	}

        Map artifactMap = project.getArtifactMap();

        assertNotNull( artifactMap, "artifact-map should not be null." );
        assertEquals( 1, artifactMap.size(), "artifact-map should contain 1 element." );

        Artifact artifact = (Artifact) artifactMap.get( key );

        assertNotNull( artifact, "dependency artifact not found in map." );

    mmHeap.addAll(Lists.newArrayList(1, 1, 2));
    assertEquals(3, mmHeap.size());
    assertFalse("Heap does not contain null", mmHeap.contains(null));
    assertFalse("Heap does not contain 3", mmHeap.contains(3));
    assertFalse("Heap does not contain 3", mmHeap.remove(3));
    assertEquals(3, mmHeap.size());
    assertTrue("Heap is not intact after remove()", mmHeap.isIntact());

The new [ParseCookie] function parses a Cookie header value and
returns all the cookies which were set in it. Since the same cookie
name can appear multiple times the returned Values can contain
more than one value for a given key.

The new [ParseSetCookie] function parses a Set-Cookie header value and

	_, ok := h[xhttp.AmzServerSideEncryption]
	// Return only true if the SSE header is specified and does not contain the SSE-KMS value
	return ok && !strings.EqualFold(h.Get(xhttp.AmzServerSideEncryption), xhttp.AmzEncryptionKMS)
}

// ParseHTTP parses the SSE-S3 related HTTP headers and checks
// whether they contain valid values.
func (sses3) ParseHTTP(h http.Header) error {

 * All comments are ignored.
 *
 * Regular lines contain fields separated by semicolons.
 *
 * The first element on each line is a single hex code point (like 0041) or a hex code point range
 * (like 0030..0039).
 *
 * The second element on each line is a mapping type, like `valid` or `mapped`.
 *
 * For lines that contain a mapping target, the next thing is a sequence of hex code points (like