Add child to sketch stage

[msamirma]

I managed to add child image as background so the users can draw on it. But my problem when i try to add intial lines or points on that sketch.

Code to add background image:
const stage = sketchReference.stage stage.addChild(backgroundImage);
Then i try to add points as intial lines
stage.addChild(linesArray)

Is there anyway to intialize child object and put lines in it?