PyTorch LightningのCallback
Callbacks should capture NON-ESSENTIAL logic that is NOT required for your lightning module to run.
https://pytorch-lightning.readthedocs.io/en/latest/extensions/callbacks.html
Trainerのcallbacks引数にCallbackのリストを渡す
https://pytorch-lightning.readthedocs.io/en/latest/common/trainer.html#callbacks
ModelCheckpoint callbacks always run last.
CallbackはリサーチコードであるLightningModule側に定義することもできる
Model-specific callbacks can also be added inside the LightningModule through configure_callbacks().
https://pytorch-lightning.readthedocs.io/en/latest/api/pytorch_lightning.core.lightning.html#pytorch_lightning.core.lightning.LightningModule.configure_callbacks