code: def __init__(self):
      super(BeamTimeBasedOutputStream).__init__()
      self._flush_event = False
      self._periodic_flusher = PeriodicThread(1, self.notify_flush)
      self._periodic_flusher.daemon = True
      self._periodic_flusher.start()
      self._output_stream = None
  
file_path: flink/flink-python/pyflink/fn_execution/beam/beam_stream_slow.py
imports: from apache_beam.coders.coder_impl import create_InputStream, create_OutputStream
  from pyflink.fn_execution.stream_slow import InputStream
  from pyflink.fn_execution.utils.operation_utils import PeriodicThread
label_desc: Use image node_id 1 to create a new BeamTimeBasedOutputStream object from inherited base classes: create_OutputStream with example: obj = BeamTimeBasedOutputStream()