编写程序，创建类MyMath，计算圆的周长和面积以及球的表面积和体积，并编写测试代码，结果均保留两位小数。

import math

class MyMath:
    
    def circle_circumference(self, radius):
        return round(2 * math.pi * radius, 2)
    
    def circle_area(self, radius):
        return round(math.pi * radius ** 2, 2)
    
    def sphere_surface_area(self, radius):
        return round(4 * math.pi * radius ** 2, 2)
    
    def sphere_volume(self, radius):
        return round((4 / 3) * math.pi * radius ** 3, 2)
    
# 测试代码
math_obj = MyMath()

# 计算圆的周长和面积
radius = 5
circumference = math_obj.circle_circumference(radius)
print("The circumference of the circle is:", circumference)

area = math_obj.circle_area(radius)
print("The area of the circle is:", area)

# 计算球的表面积和体积
radius = 3
surface_area = math_obj.sphere_surface_area(radius)
print("The surface area of the sphere is:", surface_area)

volume = math_obj.sphere_volume(radius)
print("The volume of the sphere is:", volume)