input: 
  class Sum:
      def __init__(self, x, y):
          self.x = x
          self.y = y
  
      def add(self) -> int:
          """ Calculate the sum of two integers and return the result.
          >>> Sum(3, 4).add()
          7
          >>> Sum(10, -5).add()
          5
          """
          return self.x + self.y
  
output:     
          return self.x + self.y
  