Add Memeber to Group Using Graph API

Hi,

In Azure active Directory, create some Groups and Users, now i want add add member to group using GraphAPI, but i couldn't find correct request JSON schema for this API.

Please provide me correct request JSON schema for this API.

I tried with user Entity like 

{

  "objectType": "User",
  "objectId": "83bdbe97-107a-4688-bf04-12bc959e9bf6"
}

For this request schema, i am getting the below error 

{
  "odata.error": {
    "code": "Request_BadRequest",
    "message": {
      "lang": "en",
      "value": "Error processing request stream. Type information must be specified for types that take part in inheritance."
    }
  }
}

Regards,

Veerendra