db.loadServerScripts() from mongodb shell?

Is it possible to run db.loadServerScripts() from mongodb shell? I have stored this: https://www.mongodb.com/docs/manual/tutorial/store-javascript-function-on-server/

db.system.js.insertOne(
   {
     _id : "myAddFunction" ,
     value : function (x, y){ return x + y; }
   }
);

But when I run db.loadServerScripts() from the shell the function isn't defined.