如何在环聊聊天机器人上获取媒体附件数据？

Question

我想获取有关已发送到我的Google Hangouts聊天机器人的媒体（图像）的信息。

这是我向机器人发送图像时的消息有效负载。根本没有图像信息。

{
  "name": "spaces/3IF_ggAAAAE/messages/HDdTfXFSVUI.HDdTfXFSVUI",
  "sender": {
    "name": "users/108185132749860353654",
    "displayName": "Eduardo Cauli",
    "type": "HUMAN"
  },
  "text": "",
  "cards": [],
  "previewText": "",
  "annotations": [],
  "thread": {
    "name": "spaces/3IF_ggAAAAE/threads/HDdTfXFSVUI"
  },
  "space": {
    "name": "spaces/3IF_ggAAAAE",
    "type": "DM",
    "displayName": ""
  },
  "fallbackText": "",
  "argumentText": "",
  "createTime": "2019-05-13T18:24:50.712303Z"
}