Weak self example

example.swift

        create(image: image) { [weak self] key, error in
            guard let `self` = self else {
                return
            }
            if let error = error {
                self.completion?(nil, error)
                self.completion = nil
                return
            }

            guard let key = key else {
                self.completion?(nil, self.unknownError)
                self.completion = nil
                Logging.warn("Unable to upload image")
                return
            }

            self.append(key: key, image: image, toAnnotation: annotation)
        }