def METHOD_NAME(self):
    for tag in self.params.objects("source_images"):
        params = self.params.object_params(tag)
        if params.get("random_cluster_size") == "yes":
            blacklist = list(
                map(int, params.objects("cluster_size_blacklist")))
            cluster_size = backup_utils.generate_random_cluster_size(
                blacklist)
            params["image_cluster_size"] = cluster_size
            LOG_JOB.info(
                "set image cluster size to '%s'",
                cluster_size)
        disk = self.source_disk_define_by_params(params, tag)
        disk.create(params)
        self.trash.append(disk)