AFNetworking 2.0跟踪文件上传进度

I am relatively new to AFNetworking 2.0. Using the code snippet below, I've been able to successfully upload a photo to my url. I would like to track the incremental upload progress, but I cannot find an example of doing this with version 2.0. My application is iOS 7, so I've opted for AFHTTPSessionManager.I am relatively new to AFNetworking 2.0. Using