code: def test_forward(self):
      data = torch.randn((2, 10, 40, 50))
  
      results = self.db_head(data, None, "loss")
      for i in range(3):
          self.assertEqual(results[i].shape, (2, 160, 200))
  
      results = self.db_head(data, None, "predict")
      self.assertEqual(results.shape, (2, 160, 200))
  
      results = self.db_head(data, None, "both")
      for i in range(4):
          self.assertEqual(results[i].shape, (2, 160, 200))
      self.assertTrue(torch.allclose(results[3], results[0].sigmoid()))
  
file_path: mmocr/tests/test_models/test_textdet/test_heads/test_db_head.py
imports: from unittest import TestCase
  import torch
  from mmocr.models.textdet.heads import DBHead
  from mmocr.registry import MODELS
label_desc: Use image node_id 3 for calling the TestDBHead obj's underlying member method code with example usage: obj.test_forward() without return types