removing last item in a bag

[Chan, Tim]

How do I remove the last item in a bag.

For example:

(group_1,{(2012-12-15,a),(2012-12-17,a),(2012-12-23,c)})


I would like to remove the last item so that the following is the result:


(group_1,{(2012-12-15,a),(2012-12-17,a)})