Facebook私人回复回复不提供用户id

我使用私有回复API调用在Messenger中向在Facebook上发表评论的人发送消息。如果 the doc 说我应该返回消息id和用户id,我只得到消息id作为响应:

正文: “{”id“:”m_zplkudjgaoj9wcperoavwjahycesspgmonh0sxtub8wyqrqhl0ru0y3mnimp3q7yl9rl1lfuqr0x9fynp

这是我用ruby编写的API调用代码:

url = "https://graph.facebook.com/v3.1/" + @comment_id + "/private_replies?message=" + @trigger_message + "&access_token=" + @page_access_token
                  uri = URI.parse(url)
                  https = Net::HTTP.new(uri.host,uri.port)
                  https.use_ssl = true
                  request = Net::HTTP::Post.new(uri, initheader = {'Content-Type' =>'application/json'})
                  resp = https.request(request)

为什么我不获取用户id?