# yes, this is was almost entirely copy-pasted from
# 'newer_pairwise()', this is just another convenience
# function.
"""Walk both arguments in parallel, testing if each source group is newer
than its corresponding target. Returns a pair of lists (sources_groups,
targets) where sources is newer than target, according to the semantics
of 'newer_group()'.
"""
# build a pair of lists (sources_groups, targets) where source is newer
=
=
return ,