전처리된 데이터가 있음에도 불구하고, 자꾸 오류가 발생합니다.

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "D:\anaconda\envs\mj\lib\multiprocessing\spawn.py", line 116, in spawn_main
    exitcode = _main(fd, parent_sentinel)
  File "D:\anaconda\envs\mj\lib\multiprocessing\spawn.py", line 126, in _main
    self = reduction.pickle.load(from_parent)
AttributeError: Can't get attribute 'video_dataset' on <module '__main__' (built-in)>

class video_dataset(Dataset):
    def __init__(self,frame_list,sequence_length = 16,transform = None):
        self.frame_list = frame_list
        self.transform = transform
        self.sequence_length = sequence_length
    def __len__(self):
        return len(self.frame_list)
    def __getitem__(self,idx):
        label,path = self.frame_list[idx]
        img = cv2.imread(path)
        seq_img = list()
        for i in range(16):
          img1 = img[:,128*i:128*(i+1),:]
          if(self.transform):
            img1 = self.transform(img1)
          seq_img.append(img1)
        seq_image = torch.stack(seq_img)
        seq_image = seq_image.reshape(3,16,im_size,im_size)
        return seq_image,decoder[label]

최종 오류는 이부분에서 발생합니다.

from torch.autograd import Variable
iteration = 0
acc_all = list()
loss_all = list()

for epoch in range(num_epochs):
    print('')
    print(f"--- Epoch {epoch} ---")
    phase1 = dataloaders.keys()
    for phase in phase1:
        print('')
        print(f"--- Phase {phase} ---")
        epoch_metrics = {"loss": [], "acc": []}
        for batch_i, (X, y) in enumerate(dataloaders[phase]):
            #iteration = iteration+1
            image_sequences = Variable(X.to(device), requires_grad=True)
            labels = Variable(y.to(device), requires_grad=False)
            optimizer.zero_grad()
            #model.lstm.reset_hidden_state()
            predictions = model(image_sequences)
            loss = cls_criterion(predictions, labels)
            acc = 100 * (predictions.detach().argmax(1) == labels).cpu().numpy().mean()
            loss.backward()
            optimizer.step()
            epoch_metrics["loss"].append(loss.item())
            epoch_metrics["acc"].append(acc)
            if(phase=='train'):
                lr,mom = onecyc.calc()
                update_lr(optimizer, lr)
                update_mom(optimizer, mom)
            batches_done = epoch * len(dataloaders[phase]) + batch_i
            batches_left = num_epochs * len(dataloaders[phase]) - batches_done
            sys.stdout.write(
                    "\r[Epoch %d/%d] [Batch %d/%d] [Loss: %f (%f), Acc: %.2f%% (%.2f%%)]"
                    % (
                        epoch,
                        num_epochs,
                        batch_i,
                        len(dataloaders[phase]),
                        loss.item(),
                        np.mean(epoch_metrics["loss"]),
                        acc,
                        np.mean(epoch_metrics["acc"]),
                    )
                )

                # Empty cache
            if torch.cuda.is_available():
                torch.cuda.empty_cache()

        print('')
        print('{} , acc: {}'.format(phase,np.mean(epoch_metrics["acc"])))
        torch.save(model.state_dict(),'weights_crime/c3d_{}.h5'.format(epoch))
        if(phase=='train'):
          acc_all.append(np.mean(epoch_metrics["acc"]))
          loss_all.append(np.mean(epoch_metrics["loss"]))

여러 커뮤니티에서 나오는 방법은 거의다 해봤는데 안되서 질문합니다.