Pre-trained models

[aopisco]

Currently we are using the a fixed pre-trained model. We want to allow the user to select different pre-trained models because at the moment the model has been trained using Tabula Muris Senis, so it's better suited for mouse datasets.

What needs to be done:

1. Collect annotated datasets from different species
2. Run OnClass to build those pre-trained models
3. Update code such that the user can choose/upload different pre-trained models.