Unable to play canvas streaming in Enablex. What will be canvas Selector here?

Question

I am trying to add a whiteboard in my video chat app for which i am using Enablex's canvas streaming api. https://developer.enablex.io/video-api/client-api/web-toolkit/advance-features/#start-canvas-streaming

But it is'nt working. Does canvasSelector should be something or just "CanvasElementId"

var CanvasOpt  = {
     "canvasSelector": "CanvasElementID", 
     "fps": 23
};

room.startCanvas(CanvasOpt, function(arg) {
     if(arg.result == 0) { // Success     
     }
     else { // Error arg.result == 1154 (Frame rate not supported)
     }
});

// Participant receives notification, finds stream ID 102 and plays
room.addEventListener("canvas-started", function (event) {
        var canvasStream = room.remoteStreams.get(102);
        if(canvasStream.stream !== undefined) {
             canvasStream.play("PlayerDiv");
        }
 });