MailKit API Documentation

Does any have anyone have documentation on the usage related to the

forMessageContext

and

messageContext

parameters and for the methods below? This is undocumented while public making it an unusable API.

func extensionViewController(messageContext: Data) -> MEExtensionViewController?
func primaryActionClicked(forMessageContext context: Data) async -> MEExtensionViewController? 

The APIs are located here but lack any kind of proper documentation and examples https://developer.apple.com/documentation/mailkit/memessagesecurityhandler/3882908-extensionviewcontroller