def METHOD_NAME(
        self, global_round_idx, client_num_in_total, client_num_per_round
):
    sampled_client_indexes = super().METHOD_NAME(
        global_round_idx, client_num_in_total, client_num_per_round
    )
    group_to_client_indexes = {}
    for client_idx in sampled_client_indexes:
        group_idx = self.group_indexes[client_idx]
        if not group_idx in group_to_client_indexes:
            group_to_client_indexes[group_idx] = []
        group_to_client_indexes[group_idx].append(client_idx)
    logging.info(
        "client_indexes of each group = {}".format(group_to_client_indexes)
    )
    return group_to_client_indexes