The code for Chainner has recently been restructured an a library called Spandrei created.
Spandrel is a library for loading and running pre-trained PyTorch models. It automatically detects the model architecture and hyperparameters from model files, and provides a unified interface for running models.
It is available from: https://github.com/chaiNNer-org/spandrel
This might be helpful to developers of Gimp-ML plugins