code: def _test_length(self, loader):
      self.assertEqual(len(loader), self._length)
  
file_path: avalanche/tests/benchmarks/utils/test_replay_loader.py
imports: import unittest
  import numpy
  from avalanche.benchmarks.classic import SplitMNIST
  from avalanche.benchmarks.utils.data_loader import ReplayDataLoader
label_desc: Use image node_id 4 for calling the TestReplayDataLoader obj's underlying member method code with example usage: obj._test_length(loader) without return types