class_docstr: Callback for logging hyperparameters to TensorBoard.
  
  NOTE: This callback only works in TensorFlow eager mode.
code: def _get_writer(self):
      if self._writer is None:
          raise RuntimeError(
              "hparams Keras callback cannot be reused across training sessions"
          )
      if not tf.executing_eagerly():
          raise RuntimeError(
              "hparams Keras callback only supported in TensorFlow eager mode"
          )
      return self._writer
  
file_path: tensorboard/tensorboard/plugins/hparams/_keras.py
imports: import tensorflow
  from tensorboard.plugins.hparams import api_pb2
  from tensorboard.plugins.hparams import summary
  from tensorboard.plugins.hparams import summary_v2
label_desc: Use image node_id 2 for calling the Callback obj's underlying member method code with example usage: obj._get_writer() and returns: self