code: def _check_openai_key():
      if "OPENAI_API_KEY" not in os.environ:
          raise MlflowException(
              "OPENAI_API_KEY environment variable not set",
              error_code=INVALID_PARAMETER_VALUE,
          )
  
imports: import logging
  import os
  from mlflow.exceptions import MlflowException
  from mlflow.protos.databricks_pb2 import INVALID_PARAMETER_VALUE
  from mlflow.utils.openai_utils import REQUEST_URL_CHAT, _OAITokenHolder, _OpenAIApiConfig, _OpenAIEnvVar
  from mlflow.utils.rest_utils import augmented_raise_for_status
  from mlflow.deployments import BaseDeploymentClient
label_desc: Use image node_id 4 for calling a global function with example usage: _check_openai_key() without return types