Can't understand how to do server response with vibed

[Suliman via Digitalmars-d-learn]

And the second question. Why I am getting next error after 
attempt to write to console JSON request:

Error: cannot resolve type for res.writeJsonBody(T)(T data int 
status = HTTPStatus.OK, string content_type = "application/json; 
charset=UF-8", bool allow_chunked = false)

void action(HTTPServerRequest req, HTTPServerResponse res)
{
     writeln(res.writeJsonBody);
}