Python多进程编程中，自定义元类导致类无法持久化该如何解决？

from multiprocessing import Process, Manager
from os import getpid

def process_main(cls, shared_dict, args, kwargs):
    instance = cls(*args, **kwargs)
    for attr in dir(cls):
        if not attr.startswith('__') or not attr.endswith('__') or not callable(getattr(cls, attr)):
            continue  # 只处理可调用的非特殊方法
        shared_dict[attr] = getattr(instance, attr)

class B:
    def __init__(self):
        print(f"Process {getpid()} - B.__init__")
        self.c = 'c'

    def a(self):
        print(f"Process {getpid()} - B.a")
        self.c = 'a'

class A(B):
    def __init__(self, *args, **kwargs):
        self.manager = Manager()
        self.shared_dict = self.manager.dict()
        Process(target=process_main, args=(A, self.shared_dict, args, kwargs), daemon=True).start()

    def b(self):
        print(f"Process {getpid()} - A.b")
        self.shared_dict['c'] = 'b'

    def a(self):
        print(f"Process {getpid()} - A.a")
        self.shared_dict['c'] = 'd'

    @property
    def c(self):
        return self.shared_dict.get('c')

print(f"Main process {getpid()}")
a = A()
print(f"Initial value of a.c: {a.c}")
a.b()
print(f"Value of a.c after a.b(): {a.c}")
a.a()
print(f"Value of a.c after a.a(): {a.c}")