checkpoint callbacks 
Hi
I need to save more things during checkpoint and I am using finetune_trainer.py not the pytorch lightening one, could you provide me with example on how I can modify the save part of the checkpoints? thanks 
In particular I need to define a callback with on_save function, for this I need to be able to acces "is_world_process_zero" and I am not sure how to do it. If I want to pass trainer to callback, how can I make sure this is passed? thanks<|||||>solved with understanding is_world_process_zero is accessible via  state.is_world_process_zero 