How would you rate your performance in this interview so far?

The interviewer would like to know if you are satisfied with your interview performance. If your interview were a flop, you would know, and it's much better to address outright your performance than try to sweep it under the rug.

If you feel that your performance in the interview is going well: 'I believe that this interview has been quite informative and I am happy with my performance. Is there anything that I can clarify for you from this conversation?'

If you feel that your performance in the interview is not going well: "I am not sure if I have been able to portray myself 100% accurately in this interview; although, I am trying my best. If there is anything more I can clarify for you, I would be happy to do so."