code: def testSingleWrite(self):
      self._WriteToFile("a", "abc")
      self.assertWatcherYields(["a", "b", "c"])
      self.assertFalse(self._watcher.OutOfOrderWritesDetected())
  
imports: import os
  import shutil
  import tensorflow
  from tensorboard.backend.event_processing import directory_watcher
  from tensorboard.backend.event_processing import io_wrapper
label_desc: Use image node_id 8 for calling the DirectoryWatcherTest obj's underlying member method code with example usage: obj.testSingleWrite() without return types