code: def test_nested_batch_metrics(self):
      actual = rename_doubles([["a", "a"]], [])
      expected = [["a1", "a2"]], []
      self.assertEqual(expected, actual)
  
      actual = rename_doubles([["a", "b"], "b"], [])
      expected = [["a", "b1"], "b2"], []
      self.assertEqual(expected, actual)
  
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 3 for calling the MetricsRenamingTest obj's underlying member method code with example usage: obj.test_nested_batch_metrics() without return types