code: def runebooks(summoners, optional={})
      return {} if summoners.empty?
  
      region = optional[:region] || @sightstone.region
      ids = summoners.collect { |summoner|
        if summoner.is_a? Summoner
          summoner.id
        else
          summoner
        end
      }
      uri = "https://prod.api.pvp.net/api/lol/#{region}/v1.3/summoner/#{ids.join(',')}/runes"
      response = _get_api_response(uri)
      _parse_response(response) { |resp|
        data = JSON.parse(resp)
        books = {}
        data.each do |key, raw_book|
          books[key] = RuneBook.new(raw_book)
        end
        if block_given?
          yield books
        else
          return books
        end
      }
    end
docs: returns the runebook for multiple summoners
   @param summoners [Array<(Summoner, Integer)>] list of summoner objects or ids of summoners
   @param optional [Hash<Symbol, String>] optional arguments: :region => replaces default region
   @return [Hash<Integer, Runebook>] A hash mapping runebooks to the ids of summoners