Manager().dict() garbles __init__() arguments for user-defined type passed as dict value

[eric-downes]

The following code fails

import multiprocess as mp

class UserSet(set):
    def __init__(self, y, x):
        self.y = y
        super().__init__(x)

mngr = mp.Manager()
us = UserSet(22, {23})
dproxy = mngr.dict({'x': us})

The error is

RemoteError: 
---------------------------------------------------------------------------
Traceback (most recent call last):
  File "~/.pyenv/versions/3.9.1/lib/python3.9/site-packages/multiprocess/managers.py", line 203, in handle_request
    request = c.recv()
  File "~/.pyenv/versions/3.9.1/lib/python3.9/site-packages/multiprocess/connection.py", line 259, in recv
    return _ForkingPickler.loads(buf.getbuffer())
  File "~/.pyenv/versions/3.9.1/lib/python3.9/site-packages/dill/_dill.py", line 283, in loads
    return load(file, ignore, **kwds)
  File "~/.pyenv/versions/3.9.1/lib/python3.9/site-packages/dill/_dill.py", line 278, in load
    return Unpickler(file, ignore=ignore, **kwds).load()
  File "~/.pyenv/versions/3.9.1/lib/python3.9/site-packages/dill/_dill.py", line 481, in load
    obj = StockUnpickler.load(self)
TypeError: __init__() missing 1 required positional argument: 'x'
---------------------------------------------------------------------------

Monkey-patching outside of __init__() works:

import multiprocess as mp

class UserSet(set):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

mngr = mp.Manager()
us = UserSet({23})
us.y = 22
dproxy = mngr.dict({'x':us})

This behavior occurs with mp.__version__ '0.70.11.1' on python 3.8.5 and 3.9.1

FWIW, This is in the context of attaching a lock to each value in the DictProxy.