question: Restore the best model
context: What would be the most lightning way to restore the best model? Either directly after training (in the same script) or for later use (in another script)?
  Thanks in advance !
answer: You can use the checkpont callback to save the only the best model as described here: https://williamfalcon.github.io/pytorch-lightning/Trainer/Checkpointing/ (note that that doc needs to be updated. Use save_top_k=1 instead of save_best_only)
  You can then use the load_from_checkpoint method to restore your checkpoint: https://williamfalcon.github.io/pytorch-lightning/LightningModule/methods/#load_from_metrics