code: def on_timer(
      self, timestamp: int, ctx: "KeyedProcessFunction.OnTimerContext"
  ):
      yield ctx.get_current_key(), self.state.value()
  
file_path: flink/flink-python/pyflink/examples/datastream/event_time_timer.py
imports: from pyflink.common import Time, WatermarkStrategy, Duration
  from pyflink.common.typeinfo import Types
  from pyflink.common.watermark_strategy import TimestampAssigner
  from pyflink.datastream import StreamExecutionEnvironment
  from pyflink.datastream.functions import KeyedProcessFunction, RuntimeContext
  from pyflink.datastream.state import ValueStateDescriptor, StateTtlConfig
label_desc: Use image node_id 4 for calling the Sum obj's underlying member method code with example usage: obj.on_timer(timestamp, ctx) without return types