NLP specialization- Jupyter notebook problem

Someone tell me how can I revert my notebook to the original one ?
I cannot do it with the latest checkpoint as I have saved my changes recently.
Reseting Kernel also can’t help in this case.

It’s a multi-step process.

You have to delete (or rename) your current notebook, then use the Lab Help “Get latest version” tool to give you a new copy of the original notebook.

Here’s a thread which gives the procedure Tom describes in detail.