code: def ai21_completion_call():
      try:
          messages = [
              {
                  "role": "system",
                  "content": "You are an all-knowing oracle",
              },
              {
                  "role": "user",
                  "content": "What is the meaning of the Universe?",
              },
          ]
          response = completion(
              model="j2-ultra",
              messages=messages,
              stream=True,
              max_tokens=500,
          )
          print(f"response: {response}")
          has_finished = False
          complete_response = ""
          start_time = time.time()
          for idx, chunk in enumerate(response):
              chunk, finished = streaming_format_tests(idx, chunk)
              has_finished = finished
              complete_response += chunk
              if finished:
                  break
          if has_finished is False:
              raise Exception(
                  "finished reason missing from final chunk"
              )
          if complete_response.strip() == "":
              raise Exception("Empty response received")
          print(f"completion_response: {complete_response}")
      except:
          pytest.fail(f"error occurred: {traceback.format_exc()}")
  
imports: import sys, os, asyncio
  import traceback
  import time, pytest
  from dotenv import load_dotenv
  import litellm
  from litellm import completion, acompletion, AuthenticationError, BadRequestError, RateLimitError, ModelResponse
label_desc: Use image node_id 20 for calling a global function with example usage: ai21_completion_call() without return types