input: Write a python function to calculate the perimeter of a polygon using a class. 
  assert Polygon(5).calc_perimeter() == 25
  assert Polygon(7).calc_perimeter() == 35
  assert Polygon(10).calc_perimeter() == 50
output: class Polygon:
      def __init__(self, side_length):
          self.side_length = side_length
  
      def calc_perimeter(self):
          return self.side_length * 5