code: def on_event_time(self, timer: InternalTimer):
      result = []
      timestamp = timer.get_timestamp()
      key = timer.get_key()
      self._state_backend.set_current_key(key)
      window = timer.get_namespace()
      self._trigger_context.window = window
      if self._trigger_context.on_event_time(timestamp):
          # fire
          result.append(self._emit_window_result(key, window))
  
      if self._window_assigner.is_event_time():
          self._window_function.clean_window_if_needed(
              window, timestamp
          )
      return result
  
imports: import datetime
  from abc import ABC, abstractmethod
  from typing import TypeVar, Generic, List, Dict
  import pytz
  from pyflink.common import Row, RowKind
  from pyflink.common.constants import MAX_LONG_VALUE
  from pyflink.fn_execution.datastream.timerservice import InternalTimer
  from pyflink.fn_execution.datastream.process.timerservice_impl import LegacyInternalTimerServiceImpl
  from pyflink.fn_execution.coders import PickleCoder
  from pyflink.fn_execution.table.aggregate_slow import DistinctViewDescriptor, RowKeySelector
  from pyflink.fn_execution.table.state_data_view import DataViewSpec, ListViewSpec, MapViewSpec, PerWindowStateDataViewStore
  from pyflink.fn_execution.table.window_assigner import WindowAssigner, PanedWindowAssigner, MergingWindowAssigner
  from pyflink.fn_execution.table.window_context import WindowContext, TriggerContext, K, W
  from pyflink.fn_execution.table.window_process_function import GeneralWindowProcessFunction, InternalWindowProcessFunction, PanedWindowProcessFunction, MergingWindowProcessFunction
  from pyflink.fn_execution.table.window_trigger import Trigger
  from pyflink.table.udf import ImperativeAggregateFunction, FunctionContext
label_desc: Use image node_id 5 for calling the GroupWindowAggFunctionBase obj's underlying member method code with example usage: obj.on_event_time(timer) and returns: result