code: def close(self):
      if not self._closed:
          with self._lock:
              if not self._closed:
                  self._closed = True
                  self._worker.stop()
                  self._record_writer.flush()
                  self._record_writer.close()
  
imports: from visualdl.io import bfile
  from visualdl.utils.crc32 import masked_crc32c
  from visualdl.proto import record_pb2
  import struct
  import time
  import queue
  import threading
  import os
label_desc: Use image node_id 4 for calling the _AsyncWriter obj's underlying member method code with example usage: obj.close() without return types