input: Write a python function to create an instance of a class that adds two numbers and returns the sum.
  assert Summation(5, 10).get_sum() == 15
  assert Summation(3, 7).get_sum() == 10
  assert Summation(-1, 1).get_sum() == 0
output: class Summation:
      def __init__(self, num1, num2):
          self.num1 = num1
          self.num2 = num2
      
      def get_sum(self):
          return self.num1 + self.num2