docstr: Returns the Loader class under test.
docstr_tok: ["Returns","the","Loader","class","under","test","."]
code: def _loader_class(self):
      """Returns the Loader class under test."""
      raise NotImplementedError()
  
imports: import abc
  import io
  import os
  import unittest
  from unittest import mock
  from tensorboard import test
  from tensorboard.backend.event_processing import event_file_loader
  from tensorboard.compat import tf
  from tensorboard.compat.proto import event_pb2
  from tensorboard.summary.writer import record_writer
label_desc: Use image node_id 4 for calling the EventFileLoaderTestBase obj's underlying member method code with example usage: obj._loader_class() without return types