code: def test_build_head(self):
      config = self._get_config()
      head = build_head(config)
      self.assertEqual(head.unique_id, config["unique_id"])
  
      del config["unique_id"]
      with self.assertRaises(AssertionError):
          head = build_head(config)
  
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 2 for calling the TestClassyHead obj's underlying member method code with example usage: obj.test_build_head() without return types