class_docstr: Callback for logging hyperparameters to TensorBoard.
  
  NOTE: This callback only works in TensorFlow eager mode.
code: def on_train_begin(self, logs=None):
      del logs  # unused
      with self._get_writer().as_default():
          summary_v2.hparams(self._hparams, trial_id=self._trial_id)
  
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 3 for calling the Callback obj's underlying member method code with example usage: obj.on_train_begin(logs) without return types