You review a design written by somebody else for an application and you find these: - an interface shape with a method draw() - a class circle that implements shape - a class rectangle that implements shape - a class compoundshape that: o implements interface shape o aggregates 0 or more shape objects, o has an extra method called add(shape sh) o for implementing method draw() calls the draw() method for all aggregated shape objects. you assume that a compoundshape object is made of multiple shapes. what design pattern is at work in this application? explain your answer.