what is an example of "unity" in an art painting?

https://www.google.com/search?q=signing+of+us+constitution&sxsrf=ALeKk01U-yzRdRIHJp_sBSWpcfCcgbXZiA:1592245768972&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjInNHbuYTqAhUlSTABHRbZDNgQ_AUoAXoECBwQAw&biw=1433&bih=707