Question: 
Write a function to find the volume of a sphere.


Model's Code:
def volume_sphere(radius):
    import math
    return (4/3) * math.pi * (radius ** 3)



Sample Correct Code:
import math
def volume_sphere(r):
  volume=(4/3)*math.pi*r*r*r
  return volume


Asserts:
assert volume_sphere(10)==4188.790204786391
assert volume_sphere(25)==65449.84694978735
assert volume_sphere(20)==33510.32163829113


Tests:
Test 1 of 3: PASS
Test 2 of 3: PASS
Test 3 of 3: PASS

Test 82 of 974: 62/82 (75.60975609756098%): success