[Docs] Example for auto_insert_metric_name (#12649)

Co-authored-by: Jirka Borovec <[email protected]>

Author: talregev

pytorch_lightning/callbacks/model_checkpoint.py

@@ -102,6 +102,7 @@ class ModelCheckpoint(Callback):
             For example, ``filename='checkpoint_{epoch:02d}-{acc:02.0f}`` with epoch ``1`` and acc ``1.12`` will resolve
             to ``checkpoint_epoch=01-acc=01.ckpt``. Is useful to set it to ``False`` when metric names contain ``/``
             as this will result in extra folders.
+            For example, ``filename='epoch={epoch}-step={step}-val_acc={val/acc:.2f}', auto_insert_metric_name=False``
         save_weights_only: if ``True``, then only the model's weights will be
             saved. Otherwise, the optimizer states, lr-scheduler states, etc are added in the checkpoint too.
         every_n_train_steps: Number of training steps between checkpoints.