pickling objects in jython



Hi,
The following sample code is to pickle and unpickle an object. It works fine with CPython, but the unpickling fails in Jython and I receive an error stating that "A" is unsafe to unpickle (even though I believe I have the code to make "A" safe for unpickling). What do I do wrong and how can I fix it?
Thanks,


==============================================
import sys
import cPickle
import copy_reg

class A(object):
    __slots__ = ("x","y")
    __safe_for_unpickling__ = True
    def __init__(self, a, b):
        self.x = a
        self.y = b
    def __str__(self):
        return str(self.__getstate__())
    def __reduce__(self):
        return (self.__class__.__name__, self.__getstate__())
    def __new__(cls, a, b):
        return object.__new__(cls)
    def __getnewargs__(self):
        return self.__getstate__()
    def __getstate__(self):
        return (self.x, self.y)
    def __setstate__(self, state):
        (self.x, self.y) = state

copy_reg.constructor(A)
a = A(5,"abcd")

print "Before Pickling: %s"%str(a)
mfile = open("dumptest","wb")
cPickle.dump(a,mfile,-1)
mfile.close()

mfile = open("dumptest","rb")
m = cPickle.load(mfile)
print "After Pickling: %s"%str(m)
mfile.close()
==============================================
.