code: def chat_messages():
      return [
          ChatMessage.from_system("You are a helpful assistant"),
          ChatMessage.from_user("What's the capital of France"),
      ]
  
imports: import os
  import pytest
  from openai import OpenAIError
  from haystack.components.generators.chat import OpenAIChatGenerator
  from haystack.components.generators.utils import default_streaming_callback
  from haystack.dataclasses import ChatMessage, StreamingChunk
label_desc: Use image node_id 1 for calling a global function with example usage: chat_messages() and returns: list