`ModelCheckpoint`'s argument `save_on_train_epoch_end`'s documentation unclear when value is `None`

[abhishek47kashyap]

📚 Documentation

Version 2.5.1 ModelCheckpoint's argument save_on_train_epoch_end's default value is None and its description is:

save_on_train_epoch_end (Optional[bool])
Whether to run checkpointing at the end of the training epoch.
If this is False, then the check runs at the end of the validation.

It's unclear if None is interpreted as one of True or False, or if None produces an outcome distinct from True and False.

For the sake of completeness, the documentation should specify the underlying behavior if nothing is passed in.