code: public Future<Map<Long, List<LeagueItem>>> getLeagueEntries(long... summoners) {
          return new ApiFuture<>(() -> handler.getLeagueEntries(summoners));
      }
docs: Get a listing of all league entries in the summoners' leagues
  @param summoners The ids of the summoners
  @return A map, mapping summoner ids to lists of league entries for that summoner
  @see <a href=https://developer.riotgames.com/api/methods#!/593/1863>Official API documentation</a>