class_docstr: Internal implementation of InternalTimerService.
  
  TODO: Use InternalTimerServiceImpl instead.
code: def register_processing_time_timer(self, namespace: N, t: int):
      current_key = self._keyed_state_backend.get_current_key()
      timer = (
          TimerOperandType.REGISTER_PROC_TIMER,
          InternalTimerImpl(t, current_key, namespace),
      )
      self._timers[timer] = None
  
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 5 for calling the LegacyInternalTimerServiceImpl obj's underlying member method code with example usage: obj.register_processing_time_timer(namespace, t) without return types