以下函数允许计算两个数的乘积，请稍加改造，变成可接收一个或多个数并计算乘积：

def product(*num):
    # print('len的长度：' ,len(num))
    if len(num) == 0:
        raise TypeError
    else:
        res=1
        for x in num:
            res=res*x
        return res

# 测试
print('product(5) =', product(5))
print('product(5, 6) =', product(5, 6))
print('product(5, 6, 7) =', product(5, 6, 7))
print('product(5, 6, 7, 9) =', product(5, 6, 7, 9))
if product(5) != 5:
    print('测试失败1!')
elif product(5, 6) != 30:
    print('测试失败2!')
elif product(5, 6, 7) != 210:
    print('测试失败3!')
elif product(5, 6, 7, 9) != 1890:
    print('测试失败4!')
else:
    try:
        product()
        print('测试失败5!')
    except TypeError:
        print('测试成功6!')