Is it safe to extend native classes

[cancerberoSgx]

Since I think those objects are part of the binding I wander if it's safe to implement things like

class MyPanel extends gui.Container {
constructor(){
//instantiate children, pass data, declare layout rules, here,
}
someEventHandlers(){
this.perhapsAccessingChildrenOrParent()
}
}
What about the rest of View subclasses. Should I be careful of overriding some method ? I hardly will need to do so but any comment is most appreciated.

[cancerberoSgx]

I'm closing this since gui components are not classes or at least they are not meant to be extended. (I'm getting "The constructor of this class can not be used." when calling super() in class constructor