input: Write a python function to multiply two numbers using a class.
  assert Multiplication(3, 4).multiply() == 12
  assert Multiplication(5, 6).multiply() == 30
  assert Multiplication(7, 8).multiply() == 56
output: class Multiplication:
      def __init__(self, a, b):
          self.a = a
          self.b = b
  
      def multiply(self):
          return self.a * self.b