code: def testMultipleFileLoading(self):
      self._WriteToFile("a", "a")
      self._WriteToFile("b", "b")
      self.assertLoaderYields(["a", "b"])
      self.assertLoaderYields([])
      self._WriteToFile("a", "A")
      self._WriteToFile("b", "B")
      self._WriteToFile("c", "c")
      # The loader should read new data from all the files.
      self.assertLoaderYields(["A", "B", "c"])
      self.assertLoaderYields([])
  
imports: import functools
  import glob
  import os
  import shutil
  from unittest import mock
  import tensorflow
  from tensorboard.backend.event_processing import directory_loader
  from tensorboard.backend.event_processing import directory_watcher
  from tensorboard.backend.event_processing import event_file_loader
  from tensorboard.backend.event_processing import io_wrapper
  from tensorboard.util import test_util
label_desc: Use image node_id 7 for calling the DirectoryLoaderTest obj's underlying member method code with example usage: obj.testMultipleFileLoading() without return types