I'm trying to add custome_labels to my video using facebook graph api.

I'm trying to use the following :

FB.api(
  '/{Video_ID}',
  'POST',
  {"custom_labels":"TEST"},
  function(response) {
      // Insert your code here
  }
);

The Error I'm Facing is :

{
  "error": {
    "message": "(#100) param custom_labels must be an array.",
    "type": "OAuthException",
    "code": 100,
  }
}

Any Idea how to fix this please ? Thank you !