groupby - summing multiple columns in a list of lists

[Jackson]

I'm currently using a function pasted in below. This allows me to sum
a column (index) in a list of lists.

So if mylist = [[1, 2, 3], [1, 3, 4], [2, 3, 4], [2, 4, 5]]
group_results(mylist,[0],1)

Returns:
[(1, 5), (2, 7)]

What I would like to do is allow a tuple/list of index values, rather
than a single index value to be summed up, so you could say
group_results(mylist,[0],[1,2]) would return [(1, 5,7), (2, 7,9)] but
I'm struggling to do so, any thoughts? Cheers

from itertools import groupby as gb
from operator import itemgetter as ig

def group_results(table,keys,value):
    res = []
    nkey = ig(*keys)
    value = ig(value)
    for k, group in gb(sorted(table,key=ig(*keys)),nkey):
        res.append((k,sum(value(row) for row in group)))
    return res