code: def update(self, y_pred: torch.Tensor, y_true: torch.Tensor):
      pass
  
imports: import os
  import unittest
  from unittest import skipIf
  from unittest.mock import ANY
  import numpy
  import torch
  import torch.nn
  import torchmetrics
  from poutyne import Metric, Model, do_register_metric_class, rename_doubles, unregister_metric_class
label_desc: Use image node_id 2 for calling the ConstMetric obj's underlying member method code with example usage: obj.update(y_pred, y_true) without return types