Option to return all idxmax rows in case of ties
What do you think of adding an option to « idmax » in order to return not just the first idmax but all of them in case of ties.

I think this would be really useful, especially  when used with groupby. For exemple when you want the most recent yearly published data for an entity - say a company.

We could simply add a Boolean to the function like returnTies that would be false by default.