Remove contributor through API

I am trying to remove contributors using REST API and below is my code, it doesn't give me any error but its not working either, can someone please help me understand what I am doing wrong here?

<#assign messagePostCall = restBuilder()
   .method("PUT")
   .path("/messages/${article}")
   .body({
       "type": "message",
       "contributors": {
		"type": "user",
                "id": "${contributor}",
		"contribution_method": "explicit-remove"
		}
        })
   .admin(true) />
<#assign resp = messagePostCall.call() />