text: #class class_part2 super
  
  class Animal {
  
  }
  
  class Mammal(legs) extends Animal {
    super
    this.legs = legs
  
    this.isBiped = function() {
      return this.legs == 2
    }
  }
  
  Mammal.prototype.isQuadraped = function() {
     return this.legs == 4
  }
  
  class Human extends Mammal {
    super(2)
  }
  
  var h = new Human()
  
  var m = new Mammal(4)
  
  ok(m.isQuadraped())
  ok(h.isBiped())