code: def test_init_default(self):
      component = OpenAIChatGenerator(api_key="test-api-key")
      assert component.client.api_key == "test-api-key"
      assert component.model == "gpt-3.5-turbo"
      assert component.streaming_callback is None
      assert not component.generation_kwargs
  
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 the TestOpenAIChatGenerator obj's underlying member method code with example usage: obj.test_init_default() without return types