code: def metric_func(self):
      self._metric_func = {
          "acc": max,
      }  # Those map subsentences to their optimization functions
      return self._metric_func
  
file_path: torch-points3d/torch_points3d/metrics/classification_tracker.py
imports: from typing import Dict, Any
  import torch
  import torchnet
  from torch_points3d.metrics.confusion_matrix import ConfusionMatrix
  from torch_points3d.metrics.base_tracker import BaseTracker, meter_value
  from torch_points3d.models import model_interface
label_desc: Use image node_id 7 for calling the ClassificationTracker obj's underlying member method code with example usage: obj.metric_func() and returns: self