code: def open(self):
      self.open_func()
  
imports: import abc
  from typing import cast
  from pyflink.common import Row
  from pyflink.common.serializer import VoidNamespaceSerializer
  from pyflink.datastream import TimeDomain, RuntimeContext
  from pyflink.datastream.functions import BroadcastProcessFunction
  from pyflink.datastream.window import WindowOperationDescriptor
  from pyflink.fn_execution import pickle
  from pyflink.fn_execution.datastream.process.input_handler import RunnerInputHandler, TimerHandler, _emit_results
  from pyflink.fn_execution.datastream import operations
  from pyflink.fn_execution.datastream.process.runtime_context import StreamingRuntimeContext
  from pyflink.fn_execution.datastream.process.process_function import InternalKeyedProcessFunctionOnTimerContext, InternalKeyedProcessFunctionContext, InternalProcessFunctionContext, InternalBroadcastProcessFunctionContext, InternalBroadcastProcessFunctionReadOnlyContext, InternalKeyedBroadcastProcessFunctionContext, InternalKeyedBroadcastProcessFunctionReadOnlyContext, InternalKeyedBroadcastProcessFunctionOnTimerContext
  from pyflink.fn_execution.datastream.process.timerservice_impl import TimerServiceImpl, InternalTimerServiceImpl, NonKeyedTimerServiceImpl
  from pyflink.fn_execution.datastream.window.window_operator import WindowOperator
  from pyflink.fn_execution.metrics.process.metric_impl import GenericMetricGroup
label_desc: Use image node_id 2 for calling the StatelessOperation obj's underlying member method code with example usage: obj.open() without return types