class Pool(object):

    def __init__(self):
        self.members = set()

def add_member(self, member):
    self.members.add(member)
member.pool = self
member = Member(1)
pool = Pool()
pool.add_member(member)
with open('test.pkl', 'w') as f:
    pickle.dump(member, f, pickle.HIGHEST_PROTOCOL)
with open('test.pkl', 'r') as f:
    x = pickle.load(f)
Рассол Python - как он ломается?