PyTorch cuda device pointer error ?

test.py

import multiprocessing
import multiprocessing.pool
import torch


class NoDaemonProcess(multiprocessing.Process):
    # make 'daemon' attribute always return False
    def _get_daemon(self):
        return False
    def _set_daemon(self, value):
        pass
    daemon = property(_get_daemon, _set_daemon)

class MyPool(multiprocessing.pool.Pool):
    Process = NoDaemonProcess


class Net1(torch.nn.Module):
    def __init__(self):
        super(Net1, self).__init__() 
        self.fc = torch.nn.Linear(1, 1)

def final_process(model):
    print(model)

def new_process2(model):
    pool = multiprocessing.Pool(1)
    new_process = pool.apply_async(final_process, args=(model,))
    new_process.get()
    pool.close()
    pool.join()

def new_process1():
    model = Net1().cuda()
    pool = MyPool(1)
    new_process = pool.apply_async(new_process2, args=(model,))
    new_process.get()
    pool.close() 
    pool.join()

def main():
    multiprocessing.set_start_method("spawn")
    pool = MyPool()
    new_process = pool.apply_async(new_process1)
    new_process.get()
    pool.close()
    pool.join()

if __name__ == '__main__':
    main()