code: def test_warm_up(self, mock_check_valid_model, mock_auto_tokenizer):
      generator = HuggingFaceTGIChatGenerator()
      generator.warm_up()
  
      # Assert that the tokenizer is now initialized
      assert generator.tokenizer is not None
  
imports: from unittest.mock import patch, MagicMock, Mock
  import pytest
  from huggingface_hub.inference._text_generation import TextGenerationStreamResponse, Token, StreamDetails, FinishReason
  from huggingface_hub.utils import RepositoryNotFoundError
  from haystack.components.generators.chat import HuggingFaceTGIChatGenerator
  from haystack.dataclasses import StreamingChunk, ChatMessage
label_desc: Use image node_id 4 for calling the TestHuggingFaceTGIChatGenerator obj's underlying member method code with example usage: obj.test_warm_up(mock_check_valid_model, mock_auto_tokenizer) without return types