how to sorted by summed itemgetter(x)

[Aldarion]

for example, let
from operator import itemgetter
items = [('a', [5, 2]), ('c', [1]), ('b', [6]), ('d', [7])]


sorted(items, key = itemgetter(1))
get this back:
[('c', [1]), ('a', [5, 2]), ('b', [6]), ('d', [7])]

but
sorted(items, key = sum(itemgetter(1)))
raise a errer:
'operator.itemgetter' object is not iterable

how to sorted by summed itemgetter(1)?
maybe sorted(items,key = lambda x:sum(x[1]))
can't itemgetter be used here?