input: Write a python function to create a class that squares a number.
  assert Square(2).square_number() == 4
  assert Square(5).square_number() == 25
  assert Square(12).square_number() == 144
output: def Square:
      def __init__(self, number):
          self.number = number
      
      def square_number(self):
          return self.number * self.number