gistfile1.txt

    def users(*ids_or_usernames)
      ids, usernames = [], []
      ids_or_usernames.each do |id_or_username|
        if id_or_username.is_a?(Integer)
          ids << id_or_username
        elsif id_or_username.is_a?(String)
          usernames << id_or_username
        end 
      end 
      query = {}
      query[:user_id] = ids.join(",") unless ids.empty?
      query[:screen_name] = usernames.join(",") unless usernames.empty?
      perform_get("/users/lookup.json", :query => query)
    end