How to resolve the error "Notebook validation failed: data.cells[{data__cells_x}] must be valid exactly by one definition (0 matches found)" in Jupyter Notebook?
How can I resolve the "Notebook validation failed: data.cells[{data__cells_x}] must be valid exactly by one definition (0 matches found)" error that occurs when opening a Python file in Jupyter Notebook? Additionally, when attempting to save the file, I receive the error message "The save operation succeeded, but the notebook does not appear to be valid. The validation error was: Notebook validation failed: data.cells[{data__cells_x}] must be valid exactly by one definition (0 matches found): "<UNKNOWN>". What steps should I take to troubleshoot and rectify this issue, ensuring the notebook's validity and successful saving?
