Backporting fixes:
- Docs: Make notebook templates. (#2122 by @jaheba)
- Docs: Rework installation section. (#2130 by @jaheba)
- Fix DatasetCollection for Python 3.9. (#2135 by @rsnirwan)
- Docs: Fix running tutorials for publishing docs. (#2138 by @jaheba)
- Fix PandasDataset for Python 3.9 (#2141 by @lostella)
- Fix issues with hyperparameter tuning tutorial (#2143 by @lostella)
- Docs: Apply black to notebooks. (#2144 by @jaheba)