code: def test_identity_forward(self):
      config = self._get_pass_through_config()
      head = build_head(config)
      input = torch.randn(1, config["in_plane"])
      output = head(input)
      self.assertEqual(input.size(), output.size())
      self.assert_(torch.all(torch.eq(input, output)))
  
file_path: ClassyVision/test/classy_vision_head_test.py
imports: import unittest
  import torch
  from classy_vision.heads import build_head, ClassyHead, register_head
label_desc: Use image node_id 5 for calling the TestClassyHead obj's underlying member method code with example usage: obj.test_identity_forward() without return types