code: def finish(self):
      self._metrics.put_metric(
          "fetcher_time", time.time() - self._start_time
      )
  
imports: import queue
  from itertools import chain
  import logging
  import threading
  import numpy
  import time
  from caffe2.python import workspace, core, scope, utils
  from caffe2.proto import caffe2_pb2
  from caffe2.python.parallel_workers import Metrics, State, WorkerCoordinator, GlobalWorkerCoordinator, Worker, run_worker
label_desc: Use image node_id 3 for calling the DataWorker obj's underlying member method code with example usage: obj.finish() without return types