input: Write a python function to calculate the total surface area of a cube given the side length.
  assert cube_surface_area(1) == 6
  assert cube_surface_area(2) == 24
  assert cube_surface_area(3) == 54
  assert cube_surface_area(4) == 96
output: def cube_surface_area(side_length):
      return 6 * (side_length ** 2)