code: def on_validation_start(self):
      self._setup_metrics("val")
      return super().on_validation_start()
  
imports: from abc import ABC, abstractmethod
  from typing import List, Union
  import hydra
  import torch
  from omegaconf import DictConfig, OmegaConf
  from pytorch_lightning import Trainer
  from nemo.collections.asr.metrics.audio import AudioMetricWrapper
  from nemo.core.classes import ModelPT
  from nemo.utils import logging, model_utils
label_desc: Use image node_id 6 for calling the AudioToAudioModel obj's underlying member method code with example usage: obj.on_validation_start() and returns: super