code: def test_mer(self):
      # SIT scenario
      model, optimizer, criterion, benchmark = self.init_scenario(
          multi_task=False
      )
      strategy = MER(
          model,
          optimizer,
          criterion,
          mem_size=10,
          train_mb_size=64,
          device=self.device,
          eval_mb_size=50,
          train_epochs=2,
      )
      run_strategy(benchmark, strategy)
  
      # MT scenario
      model, optimizer, criterion, benchmark = self.init_scenario(
          multi_task=True
      )
  
      strategy = MER(
          model,
          optimizer,
          criterion,
          mem_size=10,
          train_mb_size=64,
          device=self.device,
          eval_mb_size=50,
          train_epochs=2,
      )
  
      run_strategy(benchmark, strategy)
  
imports: import os
  import sys
  import unittest
  import torch
  from torch.nn import CrossEntropyLoss
  from torch.optim import SGD
  from avalanche.evaluation.metrics import StreamAccuracy, loss_metrics
  from avalanche.logging import TextLogger, InteractiveLogger
  from avalanche.models import SimpleMLP, ExpertGate
  from avalanche.models import MTSimpleMLP, IncrementalClassifier, PNN
  from avalanche.training.plugins import EvaluationPlugin, SupervisedPlugin, LwFPlugin, ReplayPlugin, RWalkPlugin, EarlyStoppingPlugin
  from avalanche.training.supervised import Naive, Replay, CWRStar, GDumb, LwF, AGEM, GEM, EWC, LFL, SynapticIntelligence, JointTraining, CoPE, StreamingLDA, MAS, BiC, MIR, ER_ACE, ER_AML, DER, LearningToPrompt, ExpertGateStrategy, MER
  from avalanche.training.supervised.cumulative import Cumulative
  from avalanche.training.supervised.icarl import ICaRL
  from avalanche.training.supervised.joint_training import AlreadyTrainedError
  from avalanche.training.supervised.strategy_wrappers import PNNStrategy
  from avalanche.training.templates import SupervisedTemplate
  from avalanche.training.templates.base import _group_experiences_by_stream
  from avalanche.training.utils import get_last_fc_layer
  from tests.training.test_strategy_utils import run_strategy
  from tests.unit_tests_utils import get_fast_benchmark, get_device
  from torchvision import transforms
label_desc: Use image node_id 6 for calling the StrategyTest obj's underlying member method code with example usage: obj.test_mer() without return types