message: address to rchao's comment
diff: @@ -1107,7 +1107,7 @@ class ModelCheckpoint(Callback):
  quantity monitored will not be overwritten. If `filepath` doesn't contain
  formatting options like `{epoch}` then `filepath` will be overwritten
  by each new better model.
  - mode: one of `{auto, min, max}`. If `save_best_only=True`, the decision to
  + mode: one of {'auto', 'min', 'max'}. If `save_best_only=True`, the decision to
  overwrite the current save file is made based on either the maximization
  or the minimization of the monitored quantity. For `val_acc`, this
  should be `max`, for `val_loss` this should be `min`, etc. In `auto`
  