code: def flush(self, epoch: int):
      if not self._testing:
          assert (
              epoch in self.expected_epochs
          ), f"{epoch} {self.expected_epochs}"
      self._flush_count += 1
  
imports: import unittest
  from typing import List
  import pytorch_lightning
  import torch
  import torch.nn
  import torch.optim
  from reagent.reporting import CompoundReporter, ReporterBase
  from reagent.training import MultiStageTrainer, ReAgentLightningModule
  from torch.utils.data import DataLoader, TensorDataset
label_desc: Use image node_id 3 for calling the DummyReporter obj's underlying member method code with example usage: obj.flush(epoch) without return types