code: def test_unfreeze():
      model = ImageClassifier(2)
      model.unfreeze()
      for p in model.backbone.parameters():
          assert p.requires_grad is True
  
imports: from typing import Any
  from unittest.mock import patch
  import pytest
  import torch
  from flash import Trainer
  from flash.core.data.io.input import DataKeys
  from flash.core.utilities.imports import _TOPIC_IMAGE_AVAILABLE, _TOPIC_SERVE_AVAILABLE
  from flash.image import ImageClassifier
  from torch import Tensor
  from tests.helpers.task_tester import TaskTester
label_desc: Use image node_id 3 for calling a global function with example usage: test_unfreeze() without return types