Allow user to choose another google account with appengine Users service

With the User engine, when the user is first prompted to log into our site using their Google account, they are shown a user interface (Google) that allows them to choose which of their Google accounts to use. This Google account is then linked to our application and they remain "subscribed" to our site until this time expires.

Is there a way to allow our users (after logging in) to change their google account they use for our site without first fetching it from all google properties (gmail, etc.)?

After reading the docs , it looks like not, but maybe someone knows a reliable hack for example. deleting certain cookies?