How to get User- email Id from hangout messages that are being sent to Rasa server after Rasa<->Google chat integration

I have integrated Rasa and google chat and able to receive a response in google chat. I am trying to get the user email id of every request I received from google chat. I am not sure how to get the user object from the response as mentioned in google chat API. It will be helpful if you can help me out.

Thanks a lot