I haven’t looked carefully, but the idea would be that someone can install pytensor and your package and use the two seamlessly. Users could combine GPU Ops from the gpu-package with Ops from the main package, or you may need rewrites to move things from CPU to GPU.
I don’t remember exactly how the GPU was controlled in Theano, so there may be some hard to work around incompatibilities. I don’t think this is a minor work though