actionscript 3 - AS3 - Overriding a class setter that doesn't exist? -

i'm following tutorial oop , setters/getters , overrides in as3.
in tutorial, have created class extends sprite act button contains shape , textfield.

the tutorial author demonstrates if use height property of class (inherited way displayobject so:

button.height = 100; 

then not shape of button scaled up, textfield , font in scaled larger. author doesn't want this, wants shape scaled up, while leaving font size way is. in following way:

override public function set height(h:number):void { // custom code here. } 

this making me confused, because having looked closely @ adobe's as3 api reference, cannot see method sets displayobject's height. can see property height.

before getting override author explain setters , getters, understand concept. however, cannot understand how can override setter doesn't seem exist?
have assumed able override anything has there in first place.

if explain technique grateful, or maybe point me more reading on this.

a property not public variable. in fact, displayobject's height property has both setter , getter function, setter exists , can overridden.