input: Write a python function to calculate the surface area of a sphere given its radius.
  assert round(sphere_surface_area(6), 5) == 452.38934
  assert round(sphere_surface_area(10), 5) == 1256.63706
  assert round(sphere_surface_area(3), 5) == 113.09734
output: def sphere_surface_area(radius):
      import math
      return 4 * math.pi * radius ** 2