docs: def container_def(image, model_data_url=None, env=None):
      """Create a definition for executing a container as part of a SageMaker model.
  
      Args:
          image (str): Docker image to run for this container.
          model_data_url (str): S3 URI of data required by this container,
              e.g. SageMaker training job model artifacts (default: None).
          env (dict[str, str]): Environment variables to set inside the container (default: None).
      Returns:
          dict[str, str]: A complete container definition object usable with the CreateModel API if passed via
          `PrimaryContainers` field.
      """
      if env is None:
          env = {}
      c_def = {'Image': image, 'Environment': env}
      if model_data_url:
          c_def['ModelDataUrl'] = model_data_url
      return c_def