3.10. Method Hiding 
By using the new modifier you can hide an inherited method with a new method of the same name. The new method may have a different signature. Method hiding is not to be confused with method overriding, because method hiding does not exhibit polymorphic behaviour.
vala
class Foo : Object {
    public void my_method() { }
}
class Bar : Foo {
    public new void my_method() { }
}You can still call the original method by casting to the base class or interface:
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void main() {
    var bar = new Bar();
    bar.my_method();
    (bar as Foo).my_method();
}