code: def mutual_friends_ids(start=1, reqnum=30, options = {})
        params = @tmpl.clone.merge(options)
        params.startindex = start
        params.reqnum = reqnum
        res = @conn.get("/api/friends/mutual_list", params.to_hash).body
        Hashie::Mash.new(JSON.parse res)
      end
docs: 互粉好友ID列表