commits: ba9f82227a9ec0c42928d5d0b978b101eda756cb

This data as json

sha	message	author_date	committer_date	raw_author	raw_committer	repo	author	committer
ba9f82227a9ec0c42928d5d0b978b101eda756cb	Modify code in "Grouped arithmetic" (#3904) `results.append(group - alt.sel(x=label))` changed to: `results.append(group - alt.sel(letters=label))`	2020-04-05T19:52:27Z	2020-04-05T19:52:27Z	4138efe426d27df6c39c0c21c04ff5e01830abf7	cd792325681cbad9f663f2879d8b69f1edbb678f	13221727	9200184	19864447