class C {
   c = "!";

   Coo() {
      return this.c;
   }
 }

class B extends C {
    b = "world";

    Boo() {
       return this.b+this.Coo();
    }
  }

export class A extends B {
  a = "hello"

  Aoo(space=" ") {
     return this.a+space;
  }

  toString() {
     return this.Aoo()+this.Boo()+this.Coo(); 
  }
}

let a = new A();
export const method_chaine = a.toString();