code: def test_vertex_ai_stream():
      load_vertex_ai_credentials()
      litellm.set_verbose = False
      litellm.vertex_project = "reliablekeys"
      import random
  
      test_models = (
          litellm.vertex_chat_models
          + litellm.vertex_code_chat_models
          + litellm.vertex_text_models
          + litellm.vertex_code_text_models
      )
      test_models = random.sample(test_models, 1)
      test_models += (
          litellm.vertex_language_models
      )  # always test gemini-pro
      for model in test_models:
          try:
              if model in [
                  "code-gecko",
                  "code-gecko@001",
                  "code-gecko@002",
                  "code-gecko@latest",
                  "code-bison@001",
                  "text-bison@001",
              ]:
                  # our account does not have access to this model
                  continue
              print("making request", model)
              response = completion(
                  model=model,
                  messages=[
                      {
                          "role": "user",
                          "content": "write 10 line code code for saying hi",
                      }
                  ],
                  stream=True,
              )
              completed_str = ""
              for chunk in response:
                  print(chunk)
                  content = chunk.choices[0].delta.content or ""
                  print("\n content", content)
                  completed_str += content
                  assert type(content) == str
                  # pass
              assert len(completed_str) > 4
          except Exception as e:
              pytest.fail(f"Error occurred: {e}")
  
file_path: litellm/litellm/tests/test_amazing_vertex_completion.py
imports: import sys, os
  import traceback
  from dotenv import load_dotenv
  import os, io
  import pytest, asyncio
  import litellm
  from litellm import embedding, completion, completion_cost, Timeout, acompletion
  from litellm import RateLimitError
  import json
  import os
  import tempfile
label_desc: Use image node_id 3 for calling a global function with example usage: test_vertex_ai_stream() without return types