question: How can I save and restore the trained model when I call fit() at pytorch_lightning every time?
context: Hi, everyone!
  I want to load model from checkpoint when start a training, and save it to disk when finished every epoch automatically,
  Is there any nice way to do that correctly?
  Shall we modify the Trianer code, or just use a special hook?
answer: For loading the model, are you looking to load just the weights? If so, take a look at LightningModule.load_from_checkpoint: https://pytorch-lightning.readthedocs.io/en/latest/common/weights_loading.html#checkpoint-loading
  
  
  Otherwise, if you want to load the whole training state (for example, including the optimizer states), take a look here: https://pytorch-lightning.readthedocs.io/en/latest/common/weights_loading.html#restoring-training-state
  
  
  For saving, take a look at the ModelCheckpoint callback: https://pytorch-lightning.readthedocs.io/en/latest/common/weights_loading.html#automatic-saving