input: Write a python function to create a Calculator class with methods for addition, subtraction, multiplication, and division.
  assert Calculator().add(3, 4) == 7
  assert Calculator().subtract(10, 5) == 5
  assert Calculator().multiply(6, 7) == 42
  assert Calculator().divide(8, 2) == 4
  assert Calculator().divide(5, 0) == ValueError
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
      
      def divide(self, a, b):
          if b == 0:
              raise ValueError("Cannot divide by zero")
          return a / b