Webform Submission Using Rest API Post method

I just created the webform and added fields.

I need to create a Webform Submission Using Rest API POST method. I just installed Rest & Rest UI modules for this.

But when I try to test my API using API tester its showing the error like this :

{"message":"Could not determine entity type bundle: \u0022webform_id\u0022 field is missing."}

But I have already determined the webform_id and here is my configuration :

POST URL : http://example.com/entity/webform_submission?_format=json

Headers :

Content-Type : application/json

POST Data :

{
  "type": {
      "webform_id": "my_form"
    },
"your_mobile":[{"value":"123456789"}],
"your_name":[{"value":"Test"}],
"your_email":[{"value":"test@gmail.com"}]
}

Drupal Version : 8.6.4
Webform Module version : 8.x-5.1

Why its not working?