def METHOD_NAME(self, tag):
    image_params = self.params.object_params(tag)
    image_chain = image_params.objects("image_backup_chain")
    self.source_images.append("drive_%s" % tag)
    self.full_backups.append("drive_%s" % image_chain[0])
    self.inc_backups.append("drive_%s" % image_chain[1])
    self.bitmaps.append("bitmap_%s" % tag)