input: Write a python function to calculate the area and circumference of a circle using the Circle class.
  assert Circle(1).area() == 3.1416
  assert Circle(1).circumference() == 6.2832
  assert Circle(5).area() == 78.54
  assert Circle(5).circumference() == 31.416
output: import math
  
  class Circle:
      def __init__(self, radius):
          self.radius = radius
  
      def area(self):
          return round(math.pi * self.radius ** 2, 4)
  
      def circumference(self):
          return round(2 * math.pi * self.radius, 4)