不能腌制< type'instancemethod'>使用多重处理Pool.map()时

我正在尝试使用multiprocessing的Pool.map()函数同时划分工作.当我使用以下代码时，它可以正常工作:

I'm trying to use multiprocessing's Pool.map() function to divide out work simultaneously. When I use the following code, it works fine:

import multiprocessing

def f(x):
    return x*x

def go():
    pool = multiprocessing.Pool(processes=4)        
    print pool.map(f, range(10))


if __name__== '__main__' :
    go()

但是，当我以一种更加面向对象的方式使用它时，它不起作用.它给出的错误消息是:

However, when I use it in a more object-oriented approach, it doesn't work. The error message it gives is:

PicklingError: Can't pickle <type 'instancemethod'>: attribute lookup
__builtin__.instancemethod failed

当以下是我的主程序时，会发生这种情况:

This occurs when the following is my main program:

import someClass

if __name__== '__main__' :
    sc = someClass.someClass()
    sc.go()

，以下是我的someClass类:

import multiprocessing

class someClass(object):
    def __init__(self):
        pass

    def f(self, x):
        return x*x

    def go(self):
        pool = multiprocessing.Pool(processes=4)       
        print pool.map(self.f, range(10))

任何人都知道问题可能是什么，或解决问题的简便方法?

Anyone know what the problem could be, or an easy way around it?