docs: def train_image(self):
          """Return the Docker image to use for training.
  
          The  :meth:`~sagemaker.estimator.EstimatorBase.fit` method, which does the model training,
          calls this method to find the image to use for model training.
  
          Returns:
              str: The URI of the Docker image.
          """
          if self.image_name:
              return self.image_name
          else:
              return create_image_uri(self.sagemaker_session.boto_region_name,
                                      self.__framework_name__,
                                      self.train_instance_type,
                                      self.framework_version,  # pylint: disable=no-member
                                      py_version=self.py_version)