# File lib/twitter/api.rb, line 635
    def follow(*args)
      options = args.extract_options!
      # Twitter always turns on notifications if the "follow" option is present, even if it's set to false
      # so only send follow if it's true
      options.merge!(:follow => true) if options.delete(:follow)
      existing_friends = Thread.new do
        friend_ids.ids
      end
      new_friends = Thread.new do
        users(args).map(&:id)
      end
      follow!(new_friends.value - existing_friends.value, options)
    end