code: def completions_response():
      return {
          "id": "7921a78e-d905-c9df-27e3-88e4831e3c3b",
          "prompt": {"text": "This is a test"},
          "completions": [
              {
                  "data": {"text": "this is a test response"},
                  "finishReason": {"reason": "length", "length": 2},
              }
          ],
      }
  
file_path: mlflow/tests/gateway/providers/test_ai21labs.py
imports: from unittest import mock
  import pytest
  from aiohttp import ClientTimeout
  from fastapi import HTTPException
  from fastapi.encoders import jsonable_encoder
  from mlflow.exceptions import MlflowException
  from mlflow.gateway.config import RouteConfig
  from mlflow.gateway.constants import MLFLOW_GATEWAY_ROUTE_TIMEOUT_SECONDS
  from mlflow.gateway.providers.ai21labs import AI21LabsProvider
  from mlflow.gateway.schemas import chat, completions, embeddings
  from tests.gateway.tools import MockAsyncResponse
label_desc: Use image node_id 5 for calling a global function with example usage: completions_response() and returns: dict