class_docstr: Internal implementation of InternalTimerService.
  
  TODO: Use InternalTimerServiceImpl instead.
code: def __init__(self, keyed_state_backend):
      self._keyed_state_backend = keyed_state_backend
      self._current_watermark = None
      self._timers = collections.OrderedDict()
  
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 1 to create a new LegacyInternalTimerServiceImpl object from inherited base classes: InternalTimerService with example: obj = LegacyInternalTimerServiceImpl(keyed_state_backend)