input: Write a python function to perform addition, subtraction, and multiplication using a class.
  assert calc.add(2, 3) == 5
  assert calc.subtract(2, 3) == -1
  assert calc.multiply(2, 3) == 6
output: class Calculator:
      def add(self, a, b):
          return a + b
  
      def subtract(self, a, b):
          return a - b
  
      def multiply(self, a, b):
          return a * b
  
  calc = Calculator()