Ionic Auth Twitter - How to get Tokens?

I started to use ionic Auth service for my ionic2 app. I need access_token and access_token_secret of users signing in through twitter. But I could not figure out where those tokens in the user data of the ionic Auth service. Here is the link for the service -> https://docs.ionic.io/services/auth/twitter-auth.html

I need user’s access_token and access_token_secret to make changes in users’ accounts on their behalf. How do I get those token and token_secret?