code: def get_key(self) -> K:
      return self._key
  
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 3 for calling the InternalTimerImpl obj's underlying member method code with example usage: obj.get_key() and returns: self