Stops protocol-specific loading of the request.
- iOS 2.0+
- macOS 10.2+
- tvOS 9.0+
- watchOS 2.0+
When this method is called, the subclass implementation should stop loading a request. This could be in response to a cancel operation, so protocol implementations must be able to handle this call while a load is in progress. When your protocol receives a call to this method, it should also stop sending notifications to the client.
Subclasses must implement this method.