code: def calculate_metrics(self, y, y_hat, tag):
      pass
  
imports: from dataclasses import dataclass, field
  from typing import Dict, List, Optional
  import pandas
  import torch
  import torch.nn
  from omegaconf import DictConfig
  from pytorch_tabular.config import DataConfig, ModelConfig, OptimizerConfig, TrainerConfig
  from pytorch_tabular.models.node import NODEBackbone
  from pytorch_tabular.tabular_model import TabularModel
  from sklearn.datasets import fetch_california_housing
  from pytorch_tabular.models import BaseModel
label_desc: Use image node_id 9 for calling the MultiStageModel obj's underlying member method code with example usage: obj.calculate_metrics(y, y_hat, tag) without return types