问题描述:
Write a function to find the circumference of a circle.

测试用例:
['assert circle_circumference(10)==62.830000000000005', 'assert circle_circumference(5)==31.415000000000003', 'assert circle_circumference(4)==25.132']

生成的代码:
import math

def circle_circumference(radius):
    return 2 * math.pi * radius