Fix typo in `fetch_dataset`

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (2357af4) 99.24% compared to head (9b297c1) 99.24%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #640 +/- ## ======================================= Coverage 99.24% 99.24% ======================================= Files 207 207 Lines 14215 14215 ======================================= Hits 14107 14107 Misses 108 108 ```

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