how to use an existing database in prediction.io

I have an existing project that uses nodejs and mongoDB (through mongoose) as the backend, and now I want to integrate all the awesomeness of prediction.io to it without touching the existing data structure, but with the current node.js SDKs I don't see how it is possible.
basically, what I want to do is use mongoose to directly interact with my database, and use the api to register actions and retrieve predictions..
so my questions here are:
* how to make prediction.io use an existing database?
* what should be the changes to make to the existing documents so that it works?

It seems that it isn't possible to use an existing database for the time being,
as it has been stated in here, the next version will make this possible.