code: def _get_group_difference(self, sp_groups):
          
          db_groups = set(Group.objects.all().values_list('name', flat=True))
          missing_from_db = set(sp_groups).difference(db_groups)
          missing_from_sp = db_groups.difference(sp_groups)
  
          return (missing_from_db, missing_from_sp)
docs: Helper method for gettings the groups that
          are present in the local db but not on stormpath
          and the other way around.