TODO: - [ ] `aggregate_numpy.py` implementation: `sum`, `mean`, `var`, `sort`. Others are already ok I think. [Done: `sum` and `mean`] - [ ] write tests - [ ] implement in other versions, or have improved exception handling.
TODO:
aggregate_numpy.pyimplementation:sum,mean,var,sort. Others are already ok I think. [Done:sumandmean]