Remark - case_1_bike_count

[jonasvdd]

I would propose to use the to_series() method as this allows for method-chaining (instead of encapsulating in the pd.Series constructor), thus increasing readability

[stijnvanhoey]

Indeed. Actually, @jorisvandenbossche, focusing more on method-chaining is worthwhile to check in general as it would increase consistency.

[jorisvandenbossche]

Yes, to_series is better here (I think our first version of the course predates this method :))
Sidenote: pandas should maybe just add a diff() method to Index as well.

[jorisvandenbossche]

Wanted to open an issue, but apparently there is already one -> pandas-dev/pandas#19708