def get_generation(searcher, tag):
    """
    Return the identifiers of all members of a population associated with
    a given searcher tag

    :param searcher:
    :param tag:
    :return:
    """
    lista = [x['_id'] for x in searcher.get_all_generations(tag) if searcher.population.is_evaluated(x['_id'])]
    return searcher.population.ids_sorted(lista)