How to determine if image is something or not?
If you already have a mouse class, you can use supervised learning. 
when you train your model, let the model learn what is a mouse by defining him that this is a specific object is mouse and define him what is not a mouse...
With this approach you just need a class of mouse to define your model and "teach" him what is a mouse, after this, your model will classify "mouse" and "not mouse"
I have a trained model that determines if an image contains either cat or dog. I'm using SVM to classify. I want a new model that determines if an image is a mouse or not. It's different from the first model that classifies into 2 classes. This new model will return TRUE or FALSE only.
I don't think I can use a classifier model since I have only 1 class; the mouse. I don't intend to use the first model or anything related to it in the 2nd model.
What is the best way to approach this?