class_docstr: This class is adapted with minor modifications from
  https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/summary/writer/writer.py#L125
  Users should not use this class directly for logging MXNet data.
  This class abstractly implements the SummaryWriter API: add_summary.
  The endpoint generates an event protobuf from the Summary object, and passes
  the event protobuf to _event_writer, which is of type EventFileWriter, for logging.
code: def _add_event(self, event, step):
      event.wall_time = time.time()
      if step is not None:
          event.step = int(step)
      self._event_writer.add_event(event)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import time
  import json
  import os
  import logging
  from .proto import event_pb2
  from .proto import summary_pb2
  from .event_file_writer import EventFileWriter
  from .summary import scalar_summary, histogram_summary, image_summary, audio_summary
  from .summary import text_summary, pr_curve_summary, _net2pb
  from .utils import _save_embedding_tsv, _make_sprite_image, _make_metadata_tsv
  from .utils import _add_embedding_config, _make_numpy_array, _get_embedding_dir
  from .utils import _is_2D_matrix
label_desc: Use image node_id 4 for calling the SummaryToEventTransformer obj's underlying member method code with example usage: obj._add_event(event, step) without return types