Xcode — DocumentAction

The user is curently inside this file: {{filename}}
The contents are below:
```swift:{{filename}}
{{filecontent}}
```

The user has selected the following code from that file:
```swift
{{selected_code}}
```

The user has asked:

Provide documentation for `{{selected_code}}`.

- Respond with a single code block.
- Only include documentation comments. No other Swift code.