## 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
callback_url = "https://example.com/api/v1/invoices/events/"
httpx.post(callback_url, json={"description": "Invoice paid", "paid": True})
```

In this case, it would be better to get **one extra server** and run some processes on it so that they all have **enough RAM and CPU time**.

       *   setFuture called on it: Neither of those can happen until we've finished processing all
       *   the completed inputs. And we're still processing at least one input, the one that
       *   triggered handleException.)
       *
       * TODO(cpovirk): Think about whether we could/should use Verify to check the return value of
       * addCausalChain.
       */

   * element, and the overall size of the collection, by one.
   *
   * <p>To both add the element and obtain the previous count of that element, use {@link
   * #add(Object, int) add}{@code (element, 1)} instead.
   *
   * @param element the element to add one occurrence of; may be null only if explicitly allowed by
   *     the implementation

import static com.google.common.collect.testing.Helpers.assertContentsInOrder;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static java.util.Arrays.asList;

		return true
	}
	return false
}

// IsPPC64CMP reports whether the op (as defined by an ppc64.A* constant) is
// one of the CMP instructions that require special handling.
func IsPPC64CMP(op obj.As) bool {
	switch op {

        List<AvPair> pairs = AvPairs.decode(fullData);

        assertNotNull(pairs, "Decoded pairs should not be null");
        assertEquals(1, pairs.size(), "Should have decoded one pair");

        AvPair pair = pairs.get(0);
        assertEquals(AvPair.MsvAvFlags, pair.getType(), "Pair type should be MsvAvFlags");
        assertTrue(pair instanceof AvFlags, "Should be decoded as AvFlags");

// the token is the last token.
//
// The value is useful to stop processing early or when it is necessary to
// deliver a final empty token (which is different from a nil token).
// One could achieve the same behavior with a custom error value but
// providing one here is tidier.
// See the emptyFinalToken example for a use of this value.
var ErrFinalToken = errors.New("final token")

			wantOk:       true,
		},
		{
			name:         "one zero, below quorum",
			m:            metaCacheEntries{inputSerialized[0], inputSerialized[0], inputSerialized[0], metaCacheEntry{}},
			r:            metadataResolutionParams{dirQuorum: 4, objQuorum: 4, strict: false},
			wantSelected: nil,
			wantOk:       false,
		},
		{
			name:         "one zero, below quorum, strict",

│   │   ├── items.py
│   │   └── users.py
│   └── internal
│       ├── __init__.py
│       └── admin.py
```

/// tip

There are several `__init__.py` files: one in each directory or subdirectory.

This is what allows importing code from one file into another.

For example, in `app/main.py` you could have a line like:

```
from app.routers import items
```

///