code: def test_epoch_end(self, outputs) -> None:
      torch.stack([x["y"] for x in outputs]).mean()
  
imports: from typing import Optional
  import torch
  from pytorch_lightning import LightningDataModule, LightningModule
  from torch.utils.data import DataLoader, Dataset, Subset
label_desc: Use image node_id 11 for calling the BoringModel obj's underlying member method code with example usage: obj.test_epoch_end(outputs) without return types