I'd say we have about 60% library code and 40% application code internally, so making it easier to write libraries is really nice. E.g. you don't want to have to write different statistical calculations for every type you use.

In particular, the fact that these types would silently give you different answers if you called `.std()` was a big headache

It was very common for us to want to be generic over pandas series and numpy arrays. A bit less so with pytorch tensors, but that was because we just aggressively converted them to numpy arrays. Fundamentally these three are all very similar types so it's frustrating to have to treat them differently.