input: Below is an instruction that describes a task. Write a response that appropriately completes the request.
  
  ### Instruction:
  Complete the Python class below so that it can calculate the sum of two integers.
  
  ### Input:
  class Sum:
      def __init__(self, x, y):
          self.x = x
          self.y = y
  
  ### Output:
  class Sum:
      def __init__(self, x, y):
          self.x = x
          self.y = y
          
      def add(self):
          return self.x + self.y
output:     def add(self):
          return self.x + self.y