code: def test_forward(self):
      config = self._get_config()
      head = build_head(config)
      input = torch.randn(1, config["in_plane"])
      output = head(input)
      self.assertEqual(output.size(), torch.Size([1, 3]))
  
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 3 for calling the TestClassyHead obj's underlying member method code with example usage: obj.test_forward() without return types