def get_backup_size(service):
  backup_files = get_snapshot_paths(service)
  total_size = sum(getsize(file) for file in backup_files)
  return total_size
Sums up the size of the snapshot files that consist the backup for the
dataset/ETHPy150Open AppScale/appscale/AppDB/backup/backup_recovery_helper.py/get_backup_size