Build a calculator using only static and class methods.

This is the way it should work:

Calculator.add(2, 4)  # 6
Calculator.subtract(8, 1)  # 7
Calculator.multiply(3, 5)  # 15
Calculator.divide(5, 2)  # 2.5

Note that I've never created an instance of the calculator. I'm using the regular class.

One final addition. The subtract method must be implemented using the add method. Something like this:

subtract = add(x, y * -1)
import unittest


class CalculatorTestCase(unittest.TestCase):

    def test_add(self):
       self.assertEqual(Calculator.add(5, 2), 7)

    def test_subtract(self):
       self.assertEqual(Calculator.subtract(5, 2), 3)

    def test_multiply(self):
       self.assertEqual(Calculator.multiply(7, 9), 63)

    def test_divide(self):
       self.assertEqual(Calculator.divide(9, 3), 3.0)

    def test_divide_decimal(self):
       self.assertEqual(Calculator.divide(9, 2), 4.5)