input: Write a Python function to manage an array of objects with add, delete, index, and size functionalities.
  assert ao.array_size() == 0
  ao.add_object("a")
  ao.add_object("b")
  assert ao.index_object(0) == "a"
  assert ao.index_object(1) == "b"
  ao.delete_object("a")
  assert ao.array_size() == 1
  assert ao.index_object(0) == "b"
output: class ArrayObjects:
      def __init__(self):
          self.objects = []
      
      def add_object(self, obj):
          self.objects.append(obj)
      
      def delete_object(self, obj):
          self.objects.remove(obj)
      
      def index_object(self, index):
          return self.objects[index]
      
      def array_size(self):
          return len(self.objects)
  
  ao = ArrayObjects()