ruff

b0905c4b - [`pycodestyle`] Handle each cell separately for `too-many-newlines-at-end-of-file` (`W391`) (#15308)

[`pycodestyle`] Handle each cell separately for `too-many-newlines-at-end-of-file` (`W391`) (#15308) Jupyter notebooks are converted into source files by joining with newlines, which confuses the check [too-many-newlines-at-end-of-file (W391)](https://docs.astral.sh/ruff/rules/too-many-newlines-at-end-of-file/#too-many-newlines-at-end-of-file-w391). This PR introduces logic to apply the check cell-wise (and, in particular, correctly handles empty cells.) Closes #13763