code: def test_before_val_epoch_dist(self, mock):
      model = nn.Sequential(
          nn.Conv2d(1, 5, kernel_size=3),
          nn.BatchNorm2d(5, momentum=0.3),
          nn.Linear(5, 10),
      )
      runner = Mock()
      runner.model = model
      hook = SyncNormHook()
      hook.before_val_epoch(runner)
  
file_path: mmdetection/tests/test_engine/test_hooks/test_sync_norm_hook.py
imports: from unittest import TestCase
  from unittest.mock import Mock, patch
  import torch.nn
  from mmdet.engine.hooks import SyncNormHook
label_desc: Use image node_id 2 for calling the TestSyncNormHook obj's underlying member method code with example usage: obj.test_before_val_epoch_dist(mock) without return types