docs: def leagues_by_summoner_ids(summoner_ids, queue=Queue.RANKED_SOLO_5x5):
      """
      Takes in a list of players ids and divide them by league tiers.
      :param summoner_ids: a list containing the ids of players
      :param queue: the queue to consider
      :return: a dictionary tier -> set of ids
      """
      summoners_league = defaultdict(set)
      for start, end in _slice(0, len(summoner_ids), 10):
          for id, leagues in get_league_entries_by_summoner(summoner_ids[start:end]).items():
              for league in leagues:
                  if Queue[league.queue]==queue:
                      summoners_league[Tier.parse(league.tier)].add(int(id))
      return summoners_league