class_docstr: Internal implementation of InternalTimerService.
  
  TODO: Use InternalTimerServiceImpl instead.
code: def advance_watermark(self, watermark: int):
      self._current_watermark = watermark
  
imports: import collections
  import time
  from enum import Enum
  from io import BytesIO
  from pyflink.common import Row
  from pyflink.datastream import TimerService
  from pyflink.fn_execution.datastream.timerservice import InternalTimer, K, N, InternalTimerService
label_desc: Use image node_id 4 for calling the LegacyInternalTimerServiceImpl obj's underlying member method code with example usage: obj.advance_watermark(watermark) without return types